UNIVERSITY  OF  CALIFORNIA. 


FROM   THE    LIBRARY   OF 

DR.  JOSEPH   LECONTE. 

GIFT  OF  MRS.   LECONTE. 

BIOLOGY 
LIBRARY 


LECTURES 


DELIVERED    TO    THE 


EMPLOYES 


Baffipre  and  Ohio  Railroad  [Sompanij 


PROF.    H.    NEWELL   MARTIN, 

Of  the  Johns  Hopkins  University, 


URS.  HENRY  SEWALL,  WM.  T.  SEDGWICK  AND  WM.  K.  BROOKS, 

Associate  Instructors  in  the  Biological  Department  of  the  University. 


FOR     FREE     DISTRIBUTION    AMONG    THE    EMPLOYES    OF    THE    BALTIMORE 
AND    OHIO    RAILROAD    COMPANY. 


LTIMORE 

PRINTED  AND  LITHOGRAPHED  BY  ISAAC  FRIEDENWALD. 
1882. 


\o-  ~> 

BIOLOGY 
IR/ 

'. 


IN  accordance  with  the  following  circular,  which  was  exten- 
sively distributed  among  the  employes  of  the  Baltimore  and  Ohio 
Railroad  Company,  a  course  of  four  lectures,  now  printed  in 
pamphlet  form,  was  delivered  in  Baltimore  in  the  month  of  Feb- 
ruary, 1882 : 

LECTURES 
For  the  Employes  of  the  Baltimore  and  Ohio  Railroad  Company. 

A  course  of  Free  Lectures,  specially  designed  for  employes  of  the 
Baltimore  and  Ohio  Railroad  Company,  will  be  delivered  in  the  month  of 
February  by  Professor  H.  Newell  Martin,  of  the  Johns  Hopkins  University, 
and  the  Associate  Instructors  in  the  Biological  Department  of  the  Univer- 
sity, as  follows  : 

Friday,  February  3 — Prof.  H.  NEWELL-  MARTIN  : 

How  Skulls  and  Backbones  are  Built. 

Friday,  February  10 — DR.  HENRY  SEWALL  : 

How  We  Move. 

Friday,  February  17 — DR.  WM.  T.  SEDGWICK  : 

On  Fermentation. 

Friday,  February  24 — DR.  WM.  K.  BROOKS  : 

Some  Curious  Kinds  of  Animal  Locomotion 

These  Lectures  will  be  delivered  in  Hollins  Hall,  corner  of  Hollins 
street  and  Carrollton  avenue,  at  8  P.  M.,  on  the  dates  named.  All  employes 
of  the  Baltimore  and  Ohio  Railroad  Company  are  cordially  invited. 

The  privilege  of  attending  these  Lectures  is  also  extended  to  the 
wives  and  daughters  of  employes  of  the  Company. 

Tickets  for  admission  to  the  course  of  Lectures  can  be  obtained  from 

MR.  A.  J.  FAIRBANK,  General  Agent,  Camden  Station. 

MR.  CASPAR  HUSSELL,  Foreman,  Bailey's. 

MR.  L.  F.  BEELER,  General  Agent,  Locust  Point. 

MR.  E.  L.  McCAHAN,  Time  Keeper,  Riverside. 

MR.  E.  E.  SHELDON,  at  the  Library  Room,  Mount  Clare,  from  12  to 
i  P.  M.  daily. 

JOHN  W.  GARRETT, 

President. 


Mr.  Garrett  was  present  on  each  occasion  and  introduced  the 
lecturers. 

At  the  conclusion  of  the  last  lecture,  which  was  delivered  on 
Friday,  February  24th,  1882,  Mr.  John  N.  Conway,  foreman  of 
the  Company's  foundry  at  Mount  Glare,  Baltimore,  offered  the 
following  resolution,  which  was  unanimously  adopted  : 

Resolved,  That  the  acknowledgments  of  the  employes  of  the  Baltimore 
and  Ohio  Railroad  Company  are  due,  and  are  hereby  tendered,  to  Mr.  John 
W.  Garrett,  President,  for  the  kindly  interest  he  has  manifested  in  their 
behalf  in  connection  with  the  course  of  Free  Lectures  arranged  for  them  by 
him  in  the  month  of  February,  1882  ;  and  that  they  desire  also  to  express 
their  acknowledgments  to  Prof.  H.  Newell  Martin,  of  the  Biological  Depart- 
ment of  the  Johns  Hopkins  University,  and  the  Associate  Instructors  in 
that  Department,  Drs.  Henry  Sewall,  Wm.  T.  Sedgwick  and  Wm.  K.  Brooks, 
for  their  kindly  co-operation,  and  for  the  practical  and  interesting  lectures 
which  they  have  delivered. 

President  Garrett  was  called  for,  and,  after  the  applause  with 
which  he  was  greeted  had  subsided,  said  : 

My  Friends  : 

When  the  suggestion  was  made  that  lectures  of  this  character  might 
prove  interesting  and  entertaining  to  the  employes  of  the  Baltimore  and 
Ohio  Railroad  Company  and  their  families,  it  was  hoped  that  result  would 
be  realized.  It  is,  therefore,  very  agreeable  to  the  President  of  the  Com- 
pany to  join  the  employes  in  their  acknowledgments  to  Prof.  Martin  and  his 
Associates  for  the  very  interesting  lectures  which  they  have  delivered. 

The  President  has  the  pleasure  of  stating  that  these  gentlemen  have 
consented  to  prepare  their  lectures,  which  will  be  printed  in  pamphlet  form, 
and  distributed  to  all  of  you  who  may  desire  to  read  and  study  them. 

It  is  hoped,  as  these  lectures  have  been  so  well  attended  and  so 
thoroughly  appreciated,  that  on  other  occasions,  and  in  other  seasons, 
arrangements  can  be  made  for  a  similar  character  of  lectures,  or  those  of  a 
like  entertaining  and  instructive  nature,  and  that  they  may  hereafter  be 
regarded  as  a  feature  connected  with  the  service  of  the  Baltimore  and  Ohio 
Railroad  Company. 

I  am  happy  to  say  that  many  celebrated  lecturers,  among  others  the 
eminent  traveller,  Mr.  Paul  du  Chaillu,  have  offered  their  services  in  con- 
nection with  the  course  of  lectures  to  the  employes  of  the  Company. 

This  pamphlet  is  printed  by  Mr.  Garrett  for  free  distribution 
among  the  employes  of  the  Baltimore  and  Ohio  Railroad  Com- 
pany. Copies  can  be  secured  by  written  or  personal  application  at 
the  President's  office  in  Baltimore. 


INTRODUCTORY  NOTE. 


The  delivery  of  the  lectures  printed  on  the  following  pages  had  an  almost 
accidental  origin.  In  the  course  of  a  conversation  one  evening  with  Presi- 
dent J.  W.  Garrett,  the  reading  room  at  Mount  Clare  Works,  which  was  estab- 
lished in  December,  1869,  and  in  which  there  are  about  1000  volumes  selected 
for  the  advantage  of  the  employes  of  the.  Baltimore  and  Ohio  Railroad  Com- 
pany, and  the  reading  room  at  Canton,  came  under  discussion.  At  these 
rooms  the  current  newspapers  and  magazines  are  provided  for  the  intel- 
lectual recreation  of  those  citizens  whose  daily  work  is  more  with  hand  than 
head,  and  whose  incomes  are  such  as  to  make  the  purchase  of  more  than  a 
small  number  of  books  impracticable.  In  consequence  o  the  generosity 
of  Mr.  Enoch  Pratt,  every  Baltimorean  will  in  future  have  the  opportunity 
to  read  at  home  any  standard  work  which  he  may  desire  to  study  ;  but  such 
was  not  the  case  at  the  time  of  the  conversation  above  referred  to. 

I  had  already  some  knowledge  of  the  working  of  the  Canton  Institute, 
based  in  part  on  personal  investigation,  and  in  part  on  conversations  with 
the  Reverend  J.  Wynne  Jones,  whose  energy  has  founded  the  Institute 
and  whose  earnestness  has  kept  it  going.  His  experience  was  that  but  a 
small  percentage  of  those  for  whose  enjoyment  the  reading  room  of  the 
Canton  Institute  was  maintained,  made  any  use  of  it.  When  I  stated  this 
to  Mr.  Garrett,  he  said  that  to  some  extent  the  same  thing  had  been  found 
in  connection  with  the  reading  room  at  Mount  Clare  Works  ;  many  local 
employes  of  the  Baltimore  and  Ohio  Railroad  used  and  enjoyed  it,  but 
many  never  came  near  it.  Reading  rooms  therefore  doing  obviously  but  a 
part  of  the  work,  the  problem  still  remained, — how  to  make  intellectual 
recreation  after  working  hours  accessible  and  attractive  to  those  who  were 
often  too  weary  to  read  magazines  or  enjoy  a  game  of  chess  or  checkers? 

As  the  conversation  proceeded,  reference  was  made  to  the  courses  of 
evening  lectures  organized  in  England  for  citizens  whose  occupation  was 
such  as  to  preclude  any  great  amount  of  thought  as  to  Art,  Literature,  or 
Science.  In  London  and  Manchester  such  lectures  had  proved  very  suc- 
cessful ;  and  Mr.  Garrett  said  that  if  such  evening  lectures  could  be  organ- 
ized in  Baltimore,  he  would  earnestly  do  what  he  could  to  promote  their 
success.  I  asked  for  a  few  days'  time  to  consult  my  colleagues  in  the  Bio- 
logical Department  of  the  Johns  Hopkins  University,  in  order  to  find  if  they 
were  willing  toco-operate  with  me  in  delivering  a  series  of  popular  scientific 
lectures.  They  all  willingly  assented. 


The  lecturers  having  been  secured,  Mr.  Garrett  undertook  to  provide  the 
lecture  hall,  and  to  pay  for  the  necessary  lantern  slides,  diagrams,  and 
assistants.  This  pamphlet,  containing  the  text  of  the  lectures  and  illustrated 
with  lithographs  of  the  figures  and  experiments  displayed,  has  been  pre- 
pared at  his  request  and  printed  at  his  expense,  in  order  that  the  lectures 
given  in  Baltimore  may  not  only  be  available  in  print  to  those  who  heard 
them,  but  may  reach  employes  of  the  Baltimore  and  Ohio  Railroad  at 
locations  far  from  Baltimore  City. 

Before  concluding,  I  take  this  opportunity  to  express,  on  behalf  of  my 
colleagues  and  myself,  our  appreciation  of  the  attention  which  our  un- 
expectedly large  audiences  gave  us.  Anticipating  but  two  or  three  hundred 
hearers,  we  were  confronted  with  six  hundred ;  and  we  fear  that  now  and 
then  the  diagrams  exhibited  were  not  of  such  size  as  to  be  distinctly  visible 
to  those  at  the  far  end  of  the  lecture  room.  Our  hearers  were,  however, 
kind  enough  to  condone  such  occasional  failings,  and  to  send  us  home  grate- 
ful to  them  and  pleased  with  ourselves.  No  one  of  us  desires  to  ever 
lecture  to  a  more  friendly  audience,  or  one  more  generous  in  its  sympathy. 

H.  NEWELL  MARTIN. 


i. 


HOW  .SKULLS  AND  BACKBONES  AftE  BUILT. 


HOW  SKULLS  AND  BACKBONES  ARE  BUILT/ 

By  H.  NEWELL  MARTIN,  M.  D.,  D.  Sc.,  M.  A. 

Professor  in  the  yohns  Hopkins  University. 


It  has  sometimes  been  my  good  fortune  to  visit  a  machine-shop, 
and  with  the  friendly  aid  of  those  there  at  work,  to  learn  some- 
thing about  the  actions  of  the  machines  and  the  uses  of  their 
different  parts.  As  the  little  knowledge  which  I  have  been  able  to 
pick  up  on  such  occasions  has  often  given  me  a  great  deal  of 
pleasure,  I  have  thought  that  I  might  perhaps  be  able,  in  turn,  to 
interest  and  entertain  you  for  an  hour  or  so  with  an  account  of  the 
structure  and  uses  of  some  parts  of  the  machines  whose  examina- 
tion is  my  business  in  life.  Just  as  there  are  many  little  things 
about  the  making  of  a  steam  engine  whose  object  and  meaning 
only  those  thoroughly  trained  to  such  work  can  appreciate,  so 
with  that  branch  of  science  called  biology  which  studies  living 
objects  :  its  followers  pry  into  a  great  many  questions  and  collect 
a  great  many  bits  of  out-of-the-way  information,  whose  interest  or 
importance  are  not  readily  made  clear  to  those  who  are  not 
biologists.  But,  on  the  other  hand,  there  are  both  in  the  structure 
and  working  of  a  locomotive,  and  in  the  structure  and  working  of 
a  living  animal,  a  great  many  things  which  any  intelligent  man  or 
woman  can  understand  and  appreciate  without  being  either  a 
practical  engineer  or  a  working  biologist.  More  especially  is  this 
true  of  the  applications  of  common  mechanical  principles  to  secure 
strength,  flexibility,  support,  and  protection  to  the  various  parts  of 
a  complicated  structure. 

Of  the  many  examples  of  the  employment  of  every-day  me- 
chanics which  we  find  in  the  bodies  of  animals,  1  have  selected  as 

*  In  the  body  of  the  lecture  I  have  acknowledged  my  indebtedness  to  Sir  Charles  Bell  ;  but  I 
desire  here  also  to  state  that  for  many  of  the  ideas  put  forth  in  it,  and  for  many  of  the  illustra- 
tions which  I  have  employed,  I  have  drawn  very  freely  upon  his  essay  on  Animal  Mechanics  — 
H.  N.  M. 


10 

the  topic  of  this  evening's  talk,  some  account  of  the  manner  in 
which  the  skeleton  is  built ;  and  then  a  little  inquiry  to  see  if  we 
can  find  out  any  reasons  for  its  being  constructed  in  the  way  it  is. 
Of  all  skeletons  that  which  interests  us  most  is,  naturally,  the  one 
which  each  of  us  has  to  use  every  day  of  his  life.  So  I  shall 
chiefly  speak  of  the  human  skeleton  ;  but  to  get  a  clear  idea  about 
it  we  must  begin  a  little  further  back,  and  think  for  a  few  minutes 
about  skeletons  in  general. 

We  all  know  what  a  skeleton  is  :  the  hard  portion  found  in  the 
bodies  of  most  animals,  serving  to  support  the  softer  parts  and 
preserve  the  shape  of  its  owner,  and  also  to  enclose  and  protect 
certain  specially  important  but  delicate  organs.  Most  animals 
may,  indeed,  be  very  well  compared  to  an  ordinary  railroad  train, 
with  its  passengers,  cars,  and  locomotive.  The  skeleton  answers  to 
the  cars  which  carry  and  pVotect  the  passengers ;  the  passengers 
are  such  things  as  eyes,  and  ears,  and  nose,  and  brain,  and 
stomach,  which  are  to  be  carried  around  in  pursuit  of  information, 
or  of  more  material  gains  (as  a  dinner),  or,  even,  of  mere  pleasure. 
The  muscles,  of  which  Dr.  Sewall  will  speak  to  you  next  week, 
move  the  skeleton  about,  and  the  skeleton  carries  the  passengers ; 
and  so  the  muscles  answer  very  well  to  the  locomotive  of  a  train. 

Now  a  good  railroad  car  must  fulfil  two  main  conditions  ;  it 
must  be  capable  of  being  moved  without  too  great  an  expenditure 
of  work,  and  it  must  provide  comfort  and  safety  for  its  passengers 
in  all  the  ordinary  and  some  of  the  extraordinary  circumstances 
of  travel.  A  good  skeleton  has  to  do  exactly  the  same  things ;  but 
with  one  important  difference.  In  a  railway  train  the  security 
of  one  passenger  is  a  matter  of  just  as  much  solicitude  to  the  com- 
pany as  that  of  any  other,  at  least  theoretically.  Some  of  us  who  are 
not  railroad  men  feel  safer  if  we  know  there  is  a  director  on  board. 
But  in  the  animal  body  that  is  not  so  :  some  of  its  passengers  are 
more  easily  injured  than  others,  and  some  are  of  far  greater 
necessity  to  the  creature  than  others  ;  and  these  especially  tender 
and  especially  important  parts  have,  what  we  may  call  special 
cars  built  for  them,  in  which  they  can  hardly  be  injured  by  any 
such  accident  as  the  body  is  at  all  likely  to  meet  with  in  its  daily  life. 

We  have  all  seen  examples  of  two  very  different  kinds  of  skele- 
tons :  those  which  have  no  soft  skin  outside  them,  and  those  which 
have.  The  anatomists  call  these  two  kinds  the  "  outside  skeleton  " 


II 


and  the  "  inside  skeleton."  In  Fig.  i*  we  see  a  familiar  creature  with 
an  outside  skeleton,  and  we  Baltimoreans,  at  least,  know  that  the 
crab  has  no  other.  From  time  to  time  he  grows  too  big  for  it,  and 
it  tears  or  splits  down  the  middle  of  the  back.  The  crab  then  creeps 
out  and  hides  away  in  some  hole  until  he  has  grown  a  new  suit  of 
armor.  In  the  intermediate  helpless  condition  he  is  caught  and 
brought  to  market  as  a  "  soft-shelled  crab  ";  and  when  the  soft  crab 
fulfils  his  natural  destiny  and  comes  to  table,  we  all  know  there  are 
no  bones  inside  to  impede  our  mastication. 


FIG.  1.   Skeleton  of  a  Crab- 


Most  of  the  higher  animals  have  an  inside  skeleton ;  it  is  less 
bulky  and  cumbersome  than  an  outer  case  and  therefore  has  certain 
advantages,  but  it  affords  less  protection :  the  latter  defect  is  partly 
compensated  for,  however,  by  the  fact  that  chambers  or  cavities  are 
hollowed  out  in  portions  of  this  inside  skeleton,  in  which  chambers 
very  delicate  organs  are  hidden  away ;  so  that  though  it  lies  inside 
the  skin  and  muscles,  it  really  is  an  outside  skeleton  to  many  parts 
whose  injury  would  be  especially  dangerous. 

*The  various  skeletons,  &c.>  represented  in  the  figures  were,  in  the  course  of  the  lecture, 
shown  on  the  screen  by  a  stereopticon. 


12 


The  foundation  of  this  internal  skeleton  is  in  most  cases  a  back- 
bone, which  usually  bears  a  skull  on  one  end  of  it ;  and  in  order  that 
we  may  all  have  some  clear  idea  as  to  what  we  are  talking  about, 
which  is  the  first  condition  of  all  talking  that  is  worth  the  doing,  I 
will  first  show  on  the  screen  a  number  of  skeletons  of  backboned 
animals. 

First  then  we  have  the  skeleton  of  a  perch  (Fig.  2),  in  which 
you  see  the  nearly  straight  backbone  running  along  the  body  of 
the  animal,  and  made  up  of  a  number  of  separate  pieces,  put  to- 
gether end  to  end.  It  bears  the  back  and  belly  fins  above  and 
below,  the  tail  fin  behind,  and  the  large  skull  in  front. 

Next  (Fig.  3)  we  have  the  skeleton  of  another  well-known  back- 
boned animal  —  the 
common  frog.  In 
it  we  find  a  short 
backbone,  made  up 
in  its  front  half  of 
a  row  of  separate 
pieces,  and  posteri- 
v  orly  of  a  long  un- 
divided slender  bone. 
It  supports  the  limbs 
and  carries  the  skull ; 
and  in  this  skull  I  can 
point  out  to  you,  bet- 
ter than  in  the  more 
complicated  one  of 
the  fish,  that  the 

brain-box  is  very  much  smaller  than  its  face  part,  which  is  made  up 
mainly  of  the  jaws  and  the  parts  which  support  them.  In  the  frog  it 
is  only  the  small  central  part,  lying  between  the  two  great  holes, 
which  are  the  sockets  for  its  big  eyes,  that  has  any  brain  *in  it.  In 
a  fish  this  is  still  more  the  case ;  it  has  a  huge  head,  but  most  of 
this  is  face,  and  very  little  indeed  is  brain-case.  In  every  animal 
with  a  bony  skull  we  find  in  fact  that  the  skull  consists  of  two 
primary  parts — brain-case  and  face -skeleton — and  the  higher  the 
animal,  as  you  will  see  when  we  proceed,  the  larger  is  the  brain- 
case  part  of  the  skull  in  proportion  to  the  face  part.  '  Some  of  you 
may  perhaps  have  already  on  other  grounds  arrived  at  the  con- 


FiG.  3.    Skeleton  of  Frog. 


14 

elusion  that  the  greatest  amount  of  "  cheek  "  is  not  always  found 
associated  with  the  largest  supply  of  brains. 

The  next  illustration  (Fig.  4)  shows  a  creature  well  known  about 
these  regions,  the  snapping  turtle.     It,  you  see,  has  both  an  inside 


FIG  .  4.    Skeleton  of  Turtle. 

skeleton  and  an  outside.  The  inside  skeleton  is  made  up  of  back- 
bone and  skull,  and  of  bones  supporting  the  limbs :  in  addition  we 
find  large  bony  plates  which  form  a  case  for  all  the  trunk  of  the 
animal,  surrounding  many  of  its  most  vital  organs.  A  turtle  is 
thus  a  good  deal  like  one  of  the  new  ironclad  men-of-war  which 


15 

European  countries  are  now  spending  their  treasure  on.  It  is 
armor-plated  about  its  most  important  regions,  but  the  less  essen- 
tial are  left  without  armor,  so  as  to  gain  in  mobility  and  lightness. 
The  brain  is  protected  by  the  skull,  so  needs  no  additional  outside 
skeleton,  and  moreover  both  it  and  the  limbs  can  be  drawn  back 
out  of  the  way  of  danger  under  the  projecting  edges  of  the  upper 
and  lower  shells  which  cover  in  the  trunk  of  the  snapper,  and  in 
this  respect  the  turtle  is  much  better  off  than  the  ironclad.  The 
turtle,  however,  carries  so  much  armor  as  to  be  impeded  by 
its  weight,  like  a  mediaeval  knight  in  his  coat  of  mail.  He 
cannot  move  about  as  actively  as  the  fish  or  frog,  and  so  misses 
a  great  many  opportunities  of  pleasure  or  profit  which  a  more 
nimble  creature  could  take  advantage  of.  The  snapper  in  fact 
suffers  from  "  over-protection,"  a  phrase  with  which  some  politi- 
cal economists  have  recently  been  making  us  pretty  well  ac- 
quainted in  connection  with  the  "  infant  industries  "  of  these  United 
States. 

Next  (Fig.  5)  we  see  the  skeleton  of  the  most  backboned  crea- 
ture in  the  world,  a  big  snake.      Here  we   find  again   a  skull 


FIG.  5.   Skeleton  of  Python  snake. 

in  front,  with  big  jaws;  and,  what  we  did  not  see  in  the  frog,  a 
great  many  pairs  of  ribs  carried  by  the  backbone. 


i6 


FIG.  6.    Skeleton  of  Eagle. 


Now  we  come  to  a  bird,  the 
American  eagle  (Fig.  6)  ;  who 
never  knowingly  turned  his 
back  on  foe  or  friend,  though  he 
has,  involuntarily,  been  rude 
to  the  artist.  In  the  eagle  we 
again  find  a  backbone  forming 
the  central  support  of  the 
whole  body,  and  bearing  the 
skull  and  limbs.  And  we  see 
the  same  thing  in  the  next 
illustration,  which  shows  the 
skeleton  of  an  ox  (Fig.  7). 

Ascending  in  the  scale  of 
backboned  animals,  we  come 
next  to  the  ape  (Fig.  8),  and 
finally  to  man  himself  (Fig. 
9),  with  his  backbone  bearing, 
as  in  the  other  cases,  a  skull 
on  one  end  and  limbs  on  the 
sides. 

So  long  as  we  look  at  the 
skull  and  spine  by  themselves, 


FIG.  7.    Skeleton  of  Ox. 


FIG.  8.   Skeleton  of  an  Ape. 

the  main  thing  which  strikes  us  is  their  function  as  .supporting  frame- 
works ;  but  if  we  now  turn  to  consider  them  in  connection  with 
the  softer  parts  of  the  body,  we  find  they  are  also  protective  cases ; 
they  conceal,  in  more  or  less  completely  closed  boxes,  some  very  im- 
portant organs.  The  eye  lies  in  a  bony  socket,  only  open  in  front ; 
the  smelling  part  of  the  nose  lies  in  a  bony  vault  near  the  forehead 
and  covered  over  by  the  "bridge"  of  the  nose;  and  the  essential 


FIG.  9.   The  human  skeleton. 


part  of  the  ear  lies  buried  away  inside  one  of  the  hardest  and 
thickest  bones  of  the  head,  the  part  of  the  ear  which  we  see  pro- 
jecting from  the  side  of  the  head  being  really  of  comparatively  little 
use.  Through  eyes,  nose,  and  ears  we  all  get  information  of  vast 
importance  to  us ;  and  the  organs  concerned  being  of  very  tender 
structure,  are  accordingly  specially  guarded  from  injury.  But  there 


are  even  more  important  parts  than  any  of  them.  Without  the 
brain,  and  the  spinal  marrow  (which  forms  a  pathway  from  the 
brain  to  most  parts  of  the  body),  eyes,  ears,  and  nose  would  be  use- 
less ;  and  these  fundamentally  important  parts,  brain  and  spinal 
marrow,  lie  far  away  from  the  surface  in  bony  chambers  built  with 
every  precaution  for  their  safety :  the  brain  in  the  skull,  and  the 
spinal  marrow  in  the  backbone.  Just 
where  these  parts  lie  in  our  own 
bodies  we  learn  from  the  next  illus- 
tration (Fig.  10),  which  represents  what 
would  be  seen  if  a  man's  body  were  di- 
vided accurately  along  the  middle  line 
into  right  and  left  halves,  and  the  cut  sur- 
face of  the  right  half  examined.  The 
bones  exposed  are  printed  in  black. 
Above  we  see  the  skull  with  its  face  parts 
comparatively  small,  and  its  brain-case 
part,  containing  the  brain  N1,  quite  large. 
From  the  brain  we  see  the  spinal  cord, 
N,  running  along  the  hollow  of  a  tube 
formed  by  the  backbone. 

Now  what  it  is  that  happens  when  we 
wish  to  move  an  arm  or  a  leg,  or  when 
we  feel  a  touch  on  hand  or  foot,  is  a  very 
complicated  matter.  But  whatever  it  is, 
it  depends  on  the  integrity  of  the  spinal 
cord ;  and  apart  from  all  theory,  certain 
broad  facts  are  certain.  When  I  will  to 
walk,  the  first  stage  in  the  process,  the 
willing,  occurs  in  the  brain :  from  the 
brain  some  result  of  my  willing  travels 
along  the  spinal  marrow,  and  from  the 
spinal  marrow,  by  certain  fine  white 

cords,  called  nerves,  to  the  muscles  which  move  my  legs.  On 
the  other  hand,  if  some  one  is  so  rude,  or  so  unfortunate,  as 
to  tread  upon  my  toes,  the  pressure  on  the  toe  starts  some- 
thing, which  travels  along  a  nerve  to  the  spinal  cord,  and  along 
the  spinal  cord  to  the  brain,  and  it  is  only  when  it  reaches  the  brain 
that  I  know  anything  about  it.  The  spinal  cord  is  therefore  an 


FIG.  JO.  Diagram  of  a  sec- 
tion along  the  middle  line  of 
the  body. 


20 

essential  link  between  our  consciousness  either  of  willing  or  feeling, 
and  the  trunk  of  the  body  or  the  limbs.  Persons  whose  spinal 
marrows  are  diseased  for  a  little  distance  in  the  upper  part  of  the 
chest  region  often  live  a  long  while ;  but  no  effort  of  their  will 
enables  them  to  move  any  part  of  the  body  below  the  level  of  the 
diseased  portion  of  the  spinal  marrow,  nor  does  any  cutting  or 
pinching  or  burning  of  parts  of  the  body  below  that  level  cause 
any  feeling.  The  spinal  cord,  therefore,  as  being  a  necessary  con- 
necting link  between  consciousness  and  most  of  the  body,  is  an 
organ  of  primary  importance ;  it  is,  to  use  our  former  illustration, 
one  of  the  passengers  in  the  railway  train  of  the  body  whose  safety 
must  be  especially  looked  after. 

If  we  come  to  consider  how  such  safety  might  best  be  secured, 
the  first  answer  would  probably  be,  put  the  spinal  marrow  in  a 
strong  bony  tube,  buried  away  from  the  surface,  and  perforated  at 
intervals  with  small  holes  to  allow  nerves  to  run  in  and  out  between 
it  and  other  parts.  But  a  rigid  rod  passing  along  a  man's  back 
and  neck  would  very  seriously  interfere  with  freedom  of  movement. 
When  we  see  a  person  with  a  stiff  and  awkward  clumsy  gait  we 
say  "  he  walks  as  if  had  swallowed  a  poker  ";  and  a  long  unbend- 
ing bone  run  down  the  middle  of  the  body  to  protect  the  spinal 
cord  would  be  in  fact  a  very  inconvenient  poker.  In  order  to  exe- 
cute agile  movements  and  maintain,  our  balance,  the  main  axis 
of  the  body  must  be  flexible.  On  the  other  hand,  if  the  protecting 
tube  in  which  the  spinal  marrow  lies  bent  sharply,  it  would  crush 
its  contents.  So  we  are  met  by  the  mechanical  problem,  how  to 
provide  a  protecting  tube  which  shall  contain  the  spinal  cord  and 
be  stiff  enough  to  support  the  body,  and  at  the  same  time  be 
flexible,  and  yet  not  able  to  bend  so  sharply  as  to  nip  the  spinal 
cord  lying  inside  it. 

Utilizing  the  hint  given  to  us  in  the  fact  that  backbones  are 
made  up  of  a  number  of  separate  pieces,  we  can  make  something 
that  fairly  well  answers  such  requirements.  I  have  here  what  was 
yesterday  a  broom-handle ;  as  you  see,  it  has  been  sawed  across 
into  a  number  of  separate  pieces,  each  about  an  inch  thick,  between 
each  piece  a  pad  of  rubber  has  been  placed,  and  the  whole  has 
been  strung  tightly  on  a  wire  to  keep  its  parts  together.  Instead 
of  the  unbending  broom-handle  we  have  now  got  a  rod  which 
is  quite  flexible ;  it  can  be  bent  to  a  considerable  extent  in  every 


21 


direction,  and  yet  it  makes  no  sharp  bend  at  any  one  point.     If  it 

were  hollow,  and  I  ran  a  piece  of  rope  down  its  middle,  the  rope 

would  bend  with  the  flexible  rod,  but  would  never  be  nipped  and 

crushed  at  a  sharp  turn. 

It  is  in  exactly  this  way  that  our  backbones   are  built ;  each  is 

made  up  of  a  number  of  separate  pieces, 

having  a  ring  at  its  back.      The  whole 

row  of  rings  makes  up  a  tube  in  which 

the  spinal  marrow  lies,  and  between  the 

rings  nerves  run  out  to  various  parts  of 

the   body.     Each  separate  piece  of  the 

backbone  is 
called  a  verte- 
bra ;  and  the 
spinal  column 
is  thus  made 
up  of  a  num- 
ber of  verte- 
brae piled  one 
on  another. 
Two  vertebrae 
from  the  mid- 
dle of  the  back 
are  shown  in 
Fig.  ii. 
You  see  that 

the  two  bones  do  not  meet  in  front ;  that 

is   because   a   soft  elastic  pad   originally 

lay  between  them,  as  the  pads  of  rubber 

between   the   bits  of  my  broom -handle, 

and  when  this  is  dissected  away  a  space 

is  left  between  the  bones.    .Behind,  bony 

bars  from  one  bone  touch  those  of  the 

other,  but  at  those  points  there  are  joints 

so  that  one  can  glide  a  little  bit  over  the 

other. 

Our  next  illustration  (Fig.   12)  shows 

a  section  made  along  the  middle  line  of 

a  fresh  spinal  column,  and  there  you  see          FlG.  &   A  section  alonff  the 

the  soft  pads  between  each  of  the  vertebrae.      middle  of  part  of  the  spinal 

column. 


PIG.  11- 


22 

We  thus  find  how  the  backbone  is  built  so  as  to  be  firm  and 
support  the  body ;  so  as  to  surround  and  protect  the  spinal  mar- 
row ;  so  as  to  be  flexible  in  all  directions,  and  yet  never  to  make 
such  a  sudden  bend  as  to  crush  the  spinal  cord  inside  it.  It  is,  I 
think  you  will  agree,  a  very  beautiful  piece  of  mechanism. 

Having  seen  how  the  spinal  marrow  is  cared  for,  we  now  pass 
on  to  consider  the  arrangements  made  to  protect  the  brain. 

The  brain-case  is  essentially  a  dome,  with  tolerably  thin  roof 
and  sides,  and  a  thicker  floor.  Now,  in  architecture  a  dome  of 
masonry  is  a  particularly  hard  thing  to  build.  The  weight  of 
its  upper  part  tends  to  make  its  sides  bulge  out  and  give  way  ; 
and  to  prevent  this  the  tiers  of  stone  in  it  have  to  be  very 
firmly  cemented  together.  In  some  domes,  as  that  of  St.  Paul's 
Cathedral  in  London,  strong  iron  chains  are  run  all  around  at 
different  levels,  imbedded  in  the  masonry;  they  serve  to  keep 
the  sides  from  being  pushed  out  by  the  weight  above.  Again, 
where  the  bottom  of  a  dome  rests  on  the  walls  which  bear  it 
there  is  a  great  tendency  for  these  to  be  pushed  apart,  by  the 
weight  of  the  dome  acting  downwards  and  outwards  along  its 
sloping  sides ;  and  •  architects  have  to  take  very  special  pre- 
cautions so  to  construct  and  support  the  walls  which  carry  the 
dome  that  they  may  be  able  to  resist  this  "lateral  thrust,"  as  it  is 
called. 

Now,  our  skulls  are  domes,  and  yet  we  know  we.  can  carry  quite 
a  heavy  weight  on  the  head,  or  bear  a  severe  blow  on  the  crown 
without  having  the  bones  crushed  in.  Only  to-day  I  saw  in  the 
New  York  Herald  a  short  paragraph  containing  an  account  (which 
may  or  may  not  be  true)  of  a  woman  who  fell  sixty  feet  down  a 
well  and  bumped  her  head  on  the  bottom,  and  yet  was  none  the 
worse  for  it ;  whether  by  knowledge  or  accident,  the  reporter  got 
the  matter  right,  for  he  wound  up  by  saying  she  was  not  injured 
"  because  she  fell  on  her  head."  The  skull  is,  in  fact,  almost  the 
strongest  part  of  the  skeleton ;  if  a  mule  kicks  a  man  on  the  arm, 
or  leg,  or  on  his  ribs,  the  usual  result  is  a  considerable  breakage ; 
but  we  all  hear  now  and  then  of  colored  brethren  who  have  risen 
up  smiling  after  a  kick  on  the  skull. 

Now  let  us  see  how  this  bony  dome  is  built  so  as  to  have  such 
strength.  Conceivably  it  might  be  made  of  one  rounded  bone, 
all  in  one  piece ;  and  so  there  could  be  no  pushing  apart  of  one 


23 

bone  from  another  when  a  blow  fell  on  the  top  of  the  head.  But 
in  that  case  our  brains  would  be  pretty  much  like  a  crab's  body, 
shut  up  in  a  case  which  could  not  grow  wider,  and  which  would 
have  to  be  shed  from  time  to  time,  as  our  brains  grew  during  early 
life,  leaving  them  in  a  "  soft-shelled  "  state  until  a  larger  skull 
could  be  again  formed  around  them.  In  Fig.  13  you  see  that 
in  fact  the  skull  is  made  up  of  a  number  of  separate  bones,  closely 


Fia.  13.   The  bones  of  the  human  skull. 


united.  These  bones  grow  at  their  edges  during  childhood,  and 
so  make  the  brain-case  bigger  as  the  brain  increases  in  size.  In 
children  there  .are  many  more  separate  pieces  in  the  skull  than 
in  a  full-grown  adult ;  and  in  advanced  old  age  some  bones 


which  you  see  in  the  figure  as  distinct  grow  together  into  one 
piece.  During  most  of  life,  however,  the  skull  dome  is  made  up 
of  many  distinct  bones  :  how  are  they  fixed  together  so  that  a 
weight  on  the  top  of  the  head  will  not  push  them  apart  ?  As  you 
see  in  the  figure  it  is  by  a  minute  and  beautiful  dovetailing,  which 
locks  together  their  margins,  so  that  the  bones  cannot  be  forced 
asunder  without  breaking  off  their  interlocked  edges. 

Next,  how  is  the  thrusting  outwards  of  the  bottom  of  the  dome- 
prevented  ?  Partly  of  course  by  the  firm  union  of  the  bones 
above  ;  but  partly  also  by  a  sort  of  buttress  on  each  side.  In 

Fig.  14  we  see  that  the  bottom  edge 
of  the  dome  rests  on  a  stout  bony 
base  ;  and  that  from  this  foundation 
a  plate  of  bone  reaches  up  on  each 
side  and  overlaps  the  lower  ends  of  the 
bones  which  form  the  sides  and  roof  of 
the  skull :  thus  they  are  prevented  from 
being  pushed  outwards.  Nor  is  this 
all.  Suppose  a  carpenter  has  to  build 
a  vaulted  roof:  we  know  that  the 
weight  of  the  roof  pushing  down  and 
outwards  on  the  walls  would  tend  to  thrust  them  apart.  This  he 
prevents  (Fig.  15)  by  putting 
in  a  "tie-beam,"  running  from 
rafter  to  rafter  across  the  roof, 
and  holding  their  lower  ends 
together.  In  the  skull  we  see 
this  same  thing.  In  figure  14 
we  see  a  tie-beam  joining  each 
side  of  the  bottom  of  the  skull 
roof;  and  in  the  living  state 
this  tie-beam  is  very  firmly  fastened  to  the  bones  on  each  side 
of  it  by  stout  cables  called  ligaments.  By  the  dovetailing  of  its 
bones,  by  the  buttresses  on  its  sides,  and  by  the  tie-beams  at  its 
base,  the  brain-case  is  thus  made  able  to  bear  heavy  blows  or 
carry  heavy  weights  without  flattening  down  and  crushing  the 
brain. 

In  the  structure  of  the  separate  bones  we  find  still,  other  arrange- 
ments to  guard  the  brain  from  injury,  as  was  pointed  out  by  Sir 


FIG.  14.   A  section  across 
the  skull. 


FIG.  15. 


25 

Charles  Bell,  to  whom  I  am  indebted  for  many  of  the  ideas  which 
I  have  the  honor  to  lay  before  you  this  evening.  Apart  from  any 
flattening  in  of  the  whole  skull,  the  brain  may  be  injured  by  an 
instrument  piercing  or  crushing  a  single  bone.  To  resist  a  sharp 
instrument  we  need  something  very  dense  and  hard,  and  calculated 
to  make  a  point  glance  off  without  penetrating.  This  is  found 
in  the  inner  layer  of  each  bone  on  the  roof  and  side  of  the  skull, 
which  is  so  hard  that  a  steel  point  will  not  readily  pierce  it.  In 
fact  its  texture  is  so  like  that  of  glass  that  anatomists  call  it  the 
glassy  layer. 

So  far,  so  good.  But  this  glassy  layer,  like  glass  itself,  is  brittle 
and  vibratile.  A  blow  on  it  would  probably^  shiver  it  into  frag- 
ments, and  even  if  it  did  not  crush  it,  would  set  it  ringing  and 
vibrating. 

If  I  strike  this  glass  bell  with  my  knuckle  you  hear  it  sounding 
for  some  time  all  over  the  room  ;  and  we  know  that  when  anything 
gives  off  sound  it  is  because  it  is  vibrating  or  shaking  very  rapidly. 
If  our  brains  were  in  such  a  glassy  case,  a  tap,  not  powerful  enough 
to  break  the  case,  might  nevertheless  set  the  skull  vibrating  and 
jar  the  brain.  How  can  this  be  prevented  ? 

When  I  take  this  damp  cloth  and  wrap  it  around  my  bell,  and 
now  again  strike  the  glass  with  my  knuckfe,  you  hear  for  each 
knock  a  dull  muffled  sound  which  ceases  at  once.  There  is  no 
continued  ringing  as  when  the  bell  was  uncovered.  We  see  then 
that  if  we  cover,  by  a  soft  damp  substance,  a  thing  which  tends  to 
keep  on  vibrating  in  consequence  of  a  blow,  we  can  .nearly  com- 
pletely prevent  its  vibration. 

This  is  just  what  we  find  in  our  skull  bones.  Outside  the  glassy 
layer  is  a  soft,  damp  layer,  and  so  a  blow  on  the  head  cannot  set 
the  bones  all  vibrating  and  jar  our  brains. 

But  the  damp  cloth  over  it  will  not  protect  my  glass  bell  from 
being  shivered  to  fragments  if  I  strike  it  with  a  heavy  hammer. 
To  protect  it  from  such  a  blow  I  must  encase.it  again  in  a  tough, 
stout  covering,  strong  enough  to  bear  the  blow  of  the  hammer, 
and  yet  not  brittle  or  it  would  be  broken  into  fragments  by  the 
stroke. 

This  case  is  represented  by  the  outermost  layer  of  our  skull 
bones,  which  is  tough,  and  fibrous,  and  strong,  pretty  much  like  a 
good  bit  of  oak  in  its  properties.  It  bears  a  pretty  severe  blow 


*^     OF  THE 


f    UNIVERSITY  ] 


26 

without  being  broken,  and  the  force  of  the  blow  is  further  weak- 
ened by  the  soft  middle  layer  under  it,  and  so  does  not  reach  the 
brittle  inner  table  with  sufficient  force  to  splinter  it.  If  you  turned 
an  ordinary  china  cup  upside  down,  covered  it  with  raw  cotton, 
and  then  fitted  a  case  of  good  tough  wood  over  the  raw  cotton,  you 
would  have  a  pretty  good  model  illustrating  how  the  skull  bones 
are  constructed.  Anything  placed  under  the  cup  would  then  be 
protected  by  the  tough  outer  layer  from  injury  by  heavy  blows 
with  a  blunt  instrument ;  by  its  hard  inner  china  layer  from  pene- 
tration by  a  sharp  instrument  which  might  pierce  the  outer  and 
middle  layers ;  and  from  jarring  by  the  soft  packing  around  the 
cup  which  would  check  its  vibration :  this  packing  also  serves  to 
greatly  weaken  the.  force  of  heavy  blows  on  the  outside  which 
mig^it  otherwise  break  the  brittle  china.  Our  brains  are  protected 
just  in  the  same  way  as  the  object  under  the  cup  would  be. 

Of  course  with  sufficient  violence  we  can  break  through  the 
skull  as  we  could  the  cup  and  its  coverings,  but  nature  only  looks 
out  for  the  average  chances,  and  does  not  provide  against  extra- 
ordinary contingencies.  None  of  us  could  carry  around  a  skull 
strong  enongh  to  resist  crushing  by  a  locomotive,  or  penetration 
by  a  bullet;  and,  anyhow,  railroad  accidents  and  rifles  were 
unknown  when  man  was  invented. 

Now,  if  you  are  not  tired  out,  I  would  like  to  point  out  to  you 
some  arrangements  in  other  parts  of  the  skeleton  which  are  also 
calculated  to  ensure  the  safety  of  this  very  important  passenger, 
the  brain.  The  brain,  as  a  passenger,  is  an  object  which  has  to  be 
carried  about  from  place  to  place;  and  you  all  know  that  man 
carries  his  brain  in  a  different  position  from  that  in  which  four- 
footed  animals  carry  theirs.  He  walks  on  one  pair  of  limbs  instead 
of  on  all-fours,  and  carries  his  skull  above  instead  of  in  front. 
No  creature,  not  even  an  ape,  walks  as  erect  as  man.  Fig.  16 
shows  the  usual  position  of  some  of  the  most  manlike  apes,  com- 
pared with  that  of  man  himself  when  walking.  An  ape  can  keep 
up  pretty  straight  for  a  short  time,  but  if  you  watch  him  you  see 
that  is  not  his  natural  mode  of  progression.  He  leans  forward, 
and  helps  himself  now  and  then  by  resting  the  hands,  at  the  ends  of 
his  very  long  arms,  on  the  ground. 

Now  if  you  saw  a  locomotive  made  like  a  bicycle,  to  run  on  two 
wheels  instead  of  four  or  six,  you  would  expect  to  find  peculiarities 


28 


in  its  structure ;  and  when  we  find  most  animals  going  on  four  legs 
and  man  on  two,  we  naturally  expect  to  find  something  in  the 
structure  of  the  human  body  which  should  be  peculiar  to  it,  and 
related  to  this  peculiar  kind  of  locomotion.  On  comparison  we  do 
find  a  good  many  such,  but  on  the  whole,  perhaps,  less  than  we 
might  have  expected.  The  general  plan  of  the  body  in  a  man,  and 
an  ape,  and  a  horse,  and  a  dog,  is  very  much  the  same ;  'only  details 
are  varied. 

One  of  these  details  is  shown  in  Fig.  17,  which  represents  the 


FIG.  17.   The  under  side  of  the  skull  of  a  man  and  of  a  gorilla. 

skull  of  a  man  and  of  a  gorilla,  both  seen  from  the  under  side. 
You  notice  that  in  man  the  bony  knobs  a  which  fit  on  to  the  top  of 
the  backbone,  and  form  the  bearings  of  the  skull,  are  nearly  in  the 
middle  of  its  under  surface.  In  the  ape  the  face  part  is  so  big  com- 
pared with  the  brain-case  part,  that  the  skull  does  not  balance  on 
the  top  of  the  backbone  as  our  skulls  very  nearly  do  ;  not  quite, 
though,  for  those  of  us  who  have  been  sinful  enough  to  go  to  sleep 
during  a  long  sermon  or  a  dull  lecture  know  the  sudden  nod  that 
wakes  us  when,  in  our  sleep,  the  muscles  holding  the  head  erect  let 
go  their  hold,  and  the  extra  weight  of  the  front  part  of  the  skull 
jerks  the  chin  down  towards  the  chest.  Our  skulls,  however,  so 
nearly  balance  on  the  top  of  the  backbone  that  we  need  but  little 
effort  to  keep  them  erect  in  the  position  which  is  necessary  for  con- 
veniently seeing  in  front  of  us  when  we  walk.  On  the  other  hand 


29 

an  ape's  badly  balanced  skull  makes  it  quite  a  labor  for  him  to  hold 
his  head  up  and  look  things  "  full  in  the  face,"  like  a  man. 

The  fact  that  our  skulls  are  carried  on  the  end  of  an  erect  spinal 
column  exposes  them  more  to  jarring  when  we  walk.  Every  time 
the  foot  reaches  the  ground  a  certain  jar  or  jerk  is  sent  up  the  bones 
of  the  legs  and  along  the  backbone  to  the  skull.  When  an  animal 
goes  on  all-fours  this  is  much  less  the  case.  The  jolt  acts  vertically, 
and  the  spinal  column  is  horizontal,  and  has  the  skull  away  at  the 
end  of  a  neck  in  front.  The  jerk  acts  across  the  length  of  the 
spinal  column  instead  of  along  it,  and  so  but  little  of  it  is  trans- 
mitted to  the  skull. 

In  connection  with  this  difference  of  natural  standing  posture  we 
find  certain  peculiarities  of  the  human  spinal  column,  calculated  to 
make  it  more  springy  and  less  liable  to  [send  jars  and  jolts  up  to 
the  skull  from  the  feet.  If  I  take  this  straight  elastic  rod,  put  one 
end  on  the  table  and  strike  the  top  end  with  a  hammer,  you  all 
readily  understand  that  the  blow  of  the  hammer  is  transmitted 
with  nearly  its  full  violence  and  suddenness  to  the  table.  But  if 
now  I  take  this  rod,  quite  like  the  other  except  that  it  is  bent,  and 
treat  it  similarly,  you  see  that  when  I  strike  its  upper  end  it  bends 
somewhat.  The  table,  instead  of  a  sudden  violent  blow,  now  gets 
only  the  more  gradual  springy  push  of  the  bending  elastic  rod. 
Now  if  you  look  back  at  the  figures  of  backbones  which  we  have 
seen  to-night  you  will  see  that  man's  is  distinguished  by  its  curva- 
tures (see  side  view,  Fig.  9).  It  is  not  curved  once  only,  but  for- 
wards in  the  neck,  back  in  the  chest,  and  forwards  again  in  the 
loins.  In  walking  it  acts  like  the  bent  rod.  The  sudden  jars  which 
might  otherwise  jolt  our  brains  are  turned  at  each  step  into  more 
gentle,  gradual  pushes  by  the  bending  springiness  of  the  curved 
backbone. 

Still  further,  we  find  in  the  construction  of  the  human  foot 
another  arrangement  to  protect  our  brains  from  that  extra  risk  of 
sudden  jolts  which  results  from  our  mode  of  walking. 

You  all  know  how  a  carriage-spring  is  built:  Two  curved 
elastic  bars  of  steel  are  fastened  together  at  their  ends,  with  their 
convex  sides  outwards.  The  axle  of  the  wheel  is  fixed  to  the 
middle  of  the  under  side  of  the  lower  rod,  and  the  weight  of  the 
carriage  bears  on  the  middle  of  the  upper  side  of  the  upper  bar. 
When  the  carriage  wheel  jolts  over  a  stone,  the  shock  transmitted 


30 

to  the  carriage  only  acts  through  the  spring:  each  curved  rod 
straightens  a  little,  and  then  gradually  resumes  its  original  shape. 
So  the  occupant  of  the  carriage,  instead  of  experiencing  a  sudden 
jerk,  feels  only  a  gentle  swaying  up  and  down.  The  arched 
springs  turn  the  sudden  movement  into  a  gradual  one. 

The  bones  of  our  feet  are  so  arranged  as  to  make  a  springy 
arch,  which  answers  to  the  upper  half  of  a  carriage-spring.  Here 
you  see  them  (Fig.iS).  When  we  walk  our  weight  bears  down  on 


FIG.  18.   Skeleton  of  the  human  foot. 

the  crown  of  the  arch  at  Ta,  where  the  leg  bone  joins  the  foot. 
This  part  of  the  arch  does  not  touch  the  ground,  but  only  the  end 
of  the  heel  bone,  Ca,  behind,  and  bones  J/at  the  roots  of  the  toes 
in  front.  The  arch  between  these  two  bearing  points  is  made  up  of 
a  number  of  small  bones,  each  of  which  can  glide  a  little  over  its 
neighbor,  and  the  whole  is  springy  and  elastic.  Hence  when  a  foot 
is  placed  violently  on  the  ground,  the  arch  yields  a  little  and  flattens 
out  under  the  sudden  pressure,  and  then  gradually  curves  up  again, 
and  thus  violent  jerks,  which  might  jar  the  whole  skeleton  up  to 
the  skull,  (as  we  know  in  fact  they  do  if  we  have  the  misfortune  to 
jump  and  come  down  on  hard  ground  on  our  heels)  are  turned, 
by  the  elasticity  of  the  arched  instep,  from  sudden  shocks  into  more 
gentle  gradual  movements  before  they  are  transmitted  to  the  rest 
of  the  body. 

And  now,  ladies  and  gentlemen,  time  is  up,  and  it  is  my  duty  to 
get  to  the  end  of  this  lecture  as  soon  as  possible.  I  have  always 
noticed  that  when  a  train  is  behind  time  the  conductor  accepts  the 
fact  with  equanimity,  though  there  is  apt  to  be  growling  among  the 
passengers.  If  I  were  of  a  vindictive  disposition  I  might  try 
get  some  little  revenge  for  sundry  "  unavoidable  detentions  " — 
that  is  the  correct  phrase,  is  it  not  ? — by  keeping  you  here  a  little 


longer ;  and  if  -you  belonged  to  the  Pennsylvania  Road,  I  believe 
I  would  try  it.  As  a  punishment  for  my  sins  I  have  had  very  often 
this  winter  to  travel  from  New  York  to  Baltimore  by  that  line,  and 
hardly  once  did  I  get  back  near  enough  schedule  time  not  to  find 
my  supper  spoiled.  But  we  all  know  the  Baltimore  and  Ohio 
never  behaves  that  way;  so  it  only  remains  for  me  to  thank  you  for 
the  courteous  manner  in  which  you  have  received  me  to-night  as 
your  conductor  over  a  short  side-branch  of  science ;  and  to  express 
the  hope  that  nothing  which  I  have  said  concerning  the  skill  and 
care  with  which  nature  has  protected  our  brains  and  spinal  cords 
will  lead  any  of  you  to  make  an  experimental  investigation  of  the 
matter  on  a  large  scale.  Nature  has  done  very  well,  but  she  has 
unfortunately  not  afforded  all  the  strength  requisite  to  bear  us  in 
safety  through  a  railroad  collision. 


II- 


HOW   WE    MOVE 


,    THE 

UNIVERSITY 

OF 


HOW  WE  MOVE.  /ft 


By  HENRY  SEWALL,  B.  Sc.,  PH.  D. 

Associate  in  Biology,  Johns  Hopkins   University. 


We  all  know  how  to  move ;  perhaps  some  of  you  will  desire  to 
put  that  simple'feat  into  practice  before  I  get  through. 

We  know  that  all  parts  of  our  bodies  may  be  moved,  but  we  are 
also  conscious  that  not  every  part  is  capable  of  moving  itself. 
Thus  the  hair  and  the  nails  never  move  alone,  and  when  the  eyes 
roll  about  you  feel  sure  that  the  eyeballs  are  moved  by  something 
outside  of  and  behind  themselves.  In  fact,  all  this  bodily  motion 
of  which  you  are  conscious  is  carried  out  by  one  definite  part  of 
the  animal  apparatus — the  muscles.  The  muscle  of  an  animal  is 
that  more  or  less  red  flesh  which  we  commonly  eat  in  beefsteak 
and  mutton-chop.  It  is  the  "  lean "  of  the  meat.  If  you  look 
carefully  at  it,  you  will  see  that  the  muscle  has  a  grain,  not  unlike 
that  of  a  deal  board;  and  if  you  pick  the  muscle  to  pieces  along 
its  grain,  you  can  separate  it  finally  into  an  immense  number  of 
very  delicate  threads,  which  can  be  no  farther  divided.  These  are 
the  ultimate  muscle  fibres,  each  of  which  is  finer  than  the  finest 
thread  of  silk  (Fig.  i).  Such  a  single  fibre  never  exists  in  the  body, 
but  muscles  as  we  see  them  are  made  up  of  an  immense  number 
of  such  tiny  threads  tightly  bound  together  side  by  side  (Fig.  2). 
So  much  for  the  living  muscle  when  it  is  at  rest.  So  far  as  I  have 
described  it  the  muscle  may  seem  to  be  nothing  but  a  peculiar 
kind  of  animal  string  or  cord.  But  there  is  a  vast  difference. 
You  know  that  a  string  may  be  cut,  or  burnt,  or  shocked  with 
electricity,  and  it  will  not  move  in  the  slightest.  But  let  us  do 
any  of  these  things  to  a  living  muscle,  and  a  most  wonderful  change 
takes  place  in  it.  Suppose  I  pass  a  shock  of  electricity  through 
one  end  of  a  muscle  fibre :  immediately  the  fibre  becomes  swelled 
and  thickened  at  that  end,  and  the  thickening  runs  along  the  whole 
length  of  the  fibre  faster  than  the  eye  can  follow,  until  the  whole 


>l  »*  »  ft**.* «*«•*•«.•«  « 


FIG.  2.   A  bundle  of  muscle  fibres,  magnified. 


I 


B'iG.  3.    a,  muscle  at  rest ;  &,  muscle  contracted. 


37 


fibre  becomes  thicker  than  before,  as  a  rope  does  when  wet  with 
water.  Compare  the  length,  now,  of  this  excited  and  thickened 
muscle  with  that  of  the  resting  and  thinner  one ;  you  will  see  that 
what  the  muscle  has  gained  in  thickness  it  has  lost  in  length  (Fig.  3). 

Therefore,     when- 
ever a  living  mus- 
cle   is     excited    it 
shortens     or    con- 
tracts, and  muscu- 
lar   contraction    is 
the  direct  cause  of 
all  the  visible  move- 
ments of  the  body. 
Now  if  this  were 
all,  muscles   could 
be  of  little  use  to  us. 
If  our  bodies  were 
made  up  simply  of 
a  soft  mass  of  mus- 
cles we  should  not 
be  able  to  do  much 
with  them.    A  per- 
son so  constructed 
might  prove  a  great  attraction, 
as -the  india-rubber  man  at  the 
Dime  Museum,  but  he  could  not 
be  of  much  use  in  a  machine  shop. 
You  know  that  when  a  heavy 
weight  is  to  be  lifted,  you  must  rest 
your  lever  or   crowbar  on  a  firm 
fulcrum  or  pivot,  upon  and  about 
which  you  turn  it.     Now,  in  the 
body,  the  muscles  work  upon  hard 
unyielding  levers  in  the  same  way ; 
the  long  bones  of  the  skeleton  are 
the  levers,  and  the  joints  mark  the 
places  of  the  fulcra.     It  is  by  pull- 
ing on  these  long  bones  and  mov- 
ing them  round  their  joints  that  the  muscles  move  the  body.  You  see 
thrown  upon  the  screen  the  shadow  of  the  living  hind  leg  and  foot 
of  a  frog  (Fig.  4).     a  is  the  calf  muscle,  which  is  fastened  at  one 


B 


FIG.  4.  A,  Frog's 
leg  with  muscles  at 
rest.  B,  Frog's  leg 
with  its  extending 
muscles  contracted. 


end  to  the  knee,  and  at  the  other  to  the  heel,  as  it  projects  back  of 
the  ankle  joint.  When  the  muscle  contracts  the  heel  is  pulled  up 
and  the  rest  of  the  foot  is  thrown  down,  turning  round  the  ankle 
joint  as  a  pivot.  This  is  one  of  the  chief  muscles  which  the 
frog  uses  when  it  leaps,  b  is  one  of  the  muscles  whose  contrac- 
tion straightens  the  knee.  Do  not  despise  this  experiment  because 
it  is  performed  on  a  frog,  for  each  of  us  depresses  his  foot  and 
raises  his  body  in  the  same  way.  When  you  stand  on  your  toes 
you  can  notice  that  the  calf  muscles  become  harder  and  thicker; 
they  are  powerful  enough  to  lift  the  whole  body  when  they  con- 
tract. All  the  kinds  of  levers  we  know  are  represented  in  the 
body.  In  the  case  just  described  the  power  was  applied  at  one 
end  of  the  foot  lever,  outside  of  the  fulcrum  and  the  weight.  But 
when  the  forearm  is  raised,  the  swelling  and  hardening  which  you 
notice  on  the  upper  surface  of  the  arm  is  caused  by  the  contrac- 
tion of  a  large  muscle  which  is  firmly  fixed  to  the  shoulder  above, 

but  below  pulls  upon  the 
bone  of  the  forearm  at  a 
spot  between  the  fulcrum 
at  the  elbow  joint  and  the 
chief  weight  to  be  lifted. 
The  manner  in  which  the 
muscle  raises  the  forearm  is 
illustrated  in  Fig.  5. 

No  doubt  you  are  dis- 
appointed that  the  whole 
matter  appears  so  little 
complicated.  It  seems  ri- 
diculously simple  that  all 
the  delicate  movements  in 
which  some  of  you  have  been  training  for  years,  are  brought  about 
merely  by  the  pulling  together  of  the  ends  of  muscle  fibres.  But  it 
is  the  grand  simplicity  of  nature.  For  without  this  contraction  of 
muscle,  not  one  work  of  man  that  exists  could  have  been  produced. 
No  thought  could  have  found  expression,  no  mighty  engines  or 
delicate  machines  would  bear  witness  to  the  splendor  of  the  human 
intellect.  If  the  muscles  of  our  hearts  and  chests  ceased  but  a  few 
seconds  to  work,  this  hall  should  be  converted  into  a  great  tomb  ; 
we  should  all  have  ceased  to  live. 

Here  is  a  little  instrument  which  may  have  a  familiar  look  to 
some  of  you  (Fig.  6).     It  is  copied  from  the  ordinary  railroad 


PIG.  5.    Movement  of  the  fore-arm :  o,  the 
muscle  at  rest ;  &,  the  muscle  contracted. 


39 


40 

• 

switch  signal.  The  disk  a  is  made  fast  to  a  movable  axis,  around 
which  a  weighted  string  is  wound.  The  muscle  is  clamped  and 
held  firmly  by  one  end  at  £,  while  the  string,  which  passes  over 
the  revolving  axis,  is  fastened  to  its  free  end.  If  the  muscle  con- 
tract it  pulls  upon  the  taut  string  which,  by  its  friction,  turns  the 
axis  over  which  it  falls,  and  with  it  the  attached  disk,  so  that  the 
latter  takes  up  a  new  position,  c  (dotted  disk  c).  The  electric 
shock  is  conveyed  through  the  muscle  by  wires,  one  of  which  is 
made  fast  to  each  end.  If,  then,  the  muscle  contract  the  disk 
flies  up,  and  when  the  shortening  is  over  the  disk  regains  its  hori- 
zontal position,  being  pulled  down  by  the  weighted  string.  Notice 
that  every  time  I  send  into  the  muscle  a  single  shock  the  muscle 
answers  by  a  single  rapid  contraction,  occupying  from  first  to  last 
not  more  than  TO  second,  and  there  are  just  as  many  contractions 
as  there  are  shocks,  and  no  more.  The  same  is  the  case  with  our 
own  muscles ;  one  shock  of  electricity  would  cause  in  them  one 
fleeting  spasm  only.  It  is  very  evident  that  such  a  kind  of  motion 
should  be  of  little  use  to  us.  A  person  with  St.  Vitus'  dance  could 
hardly  become  a  good  machinist.  How  is  it,  then,  that  we  are 
capable  of  such  regular,  even,  long-continued  contractions  as  is  the 
case  ?  In  the  same  way,  probably,  as  I  was  able  to  show  you  a 
steady,  long-continued  contraction  of  the  frog's  muscle  on  the 
screen,  and  that  is  very  simple.  Suppose  when  a  muscle  is  at 
rest  it  is  of  the  length  represented  in  a  of  Fig.  7.  Give  it  a  shock, 


FIG.  7.    Showing  how  fleeting  single  contractions  may  be  heaped  together  to  form 
long-continued  ones. 


41 

and  it  takes  the  form  b ;  shock  it  again  before  it  has  had  time  to 
relax  and  it  contracts  still  further  to  the  form  <:,  and  so  on  until  the 
muscle  can  shorten  no  farther  ;  then  'a  continuation  of  the  electric 
shocks  serves  simply  to  keep  the  muscle  in  that  steady,  uniform 
state  of  contraction.  You  notice  that  I  can  produce  this  effect  on 
the  railroad  signal.  When  the  shocks  succeed  each  other  slowly 
the  disk  simply  moves  up  and  down,  but  as  the  succession  of  excite- 
ments becomes  gradually  more  rapid  the  disk  oscillates  less  and  less, 
moving  higher,  till  finally  it  reaches  the  top  of  its  path  and  stops 
there,  showing  that  the  muscle  is  in  a  state  of  steady  contraction. 

When  one  makes  a  voluntary  motion,  the  will  sends  along  the 
nerves  (of  which  I  will  speak  to  you  in  a  moment)  a  succession  of 
excitements,  of  what  kind  we  know  not,  and  these  stir  up  the 
muscle  in  the  manner  described.  When  the  will  is  weak,  or  the 
body  diseased,  when  one  suffers  from  terror  or  emotion  of  any 
kind,  when  a  man  visits  the  dram  shop  too  often  and  cares  more 
about  his  bottle  than  a  good  constitution,  you  will  notice  that  that 
person's  movements  lose  their  natural  smoothness,  and  when  he 
lifts  his  hand  it  is  shaking.  That  simply  means  that  his  will  is  not 
able  to  send  to  the  muscles  a  regular  succession  of  impulses  to 
excite  them.  It  happens  no  doubt  in  a  way  which  we  are  able  to 
imitate  on  our  railroad  signal,  Fig.  6.  You  see  that  when  the 
shocks  succeed  each  other  rapidly  at  regular  intervals,  the  disk 
remains  steady  in  the  upper  part  of  its  path,  but  so  soon  as  the 
succession  of  shocks  becomes  irregular,  the  disk  begins  to  shake 
back  and  forth  like  a  trembling  hand. 

You  all  know  what  a  machine  is.  Broadly  speaking,  it  is  an  ap- 
paratus to  do  work.  Perhaps  you  have  seen  enough  to  believe 
that  the  muscle  answers  this  definition,  and  is  a  true  machine,  for 
it  can  lift  and  carry  burdens  and  do  work.  The  ^  efficiency  of  an 
engine  is  measured  by  the  amount  of  work  that  one  can  get  out  of 
it  by  burning  a  certain  amount  of  coal.  For  the  best  engines  that 
man  has  made,  this  ratio  is  about  one-tenth.  That  is,  of  all  the 
heat  made  by  burning  its  coal  an  engine  can  turn  only  TO  into 
work,  the  other  T9o  being  lost  as  heat.  But  nature's  engine,  the 
muscle,  is  more  efficient  than  this.  As  nearly  as  can  be  calculated, 
more  than  i  of  the  energy  which  the  muscle  expends  in  contraction 
goes  to  doing  work. 

We  have  been  getting  a  good  deal  of  work  out  of  this 
muscle  engine,  and  that  energy  must  have  been  stored  up  as 


42 

fuel  in  the  muscle  substance.  The  change  which  takes  place 
in  it  on  being  excited  is  a  good  deal  like  that  which  happens  on 
the  explosion  of  a  charge  of  gunpowder.  Energy  was  stored  up 
in  the  charge,  and  then  all  at  once  set  free  when  the  powder  was 
ignited.  Notice  further  this  peculiar  property  of  each — that  the 
amount  of  work  gotten  out  of  either  powder  or  muscle  is  indepen- 
dent of  the  amount  of  energy  you  apply  to  set  free  that  energy  which 
is  stored  in  either.  A  small  percussion  cap  can  fire  off  a  barrel  of 
gunpowder  as  easily  as  could  the  heat  of  a  volcano.  In  like  manner 
the  electric  current  we  have  used  to  stir  up  this  muscle  could  not 
itself  accomplish  more  than  a  small  fraction  of  the  work  it  causes  the 
muscle  to  do.  But  the  muscle  has  more  remarkable  powers  still. 
It  is  a  store  of  energy,  as  the  gunpowder  is.  But  you  know  that 
if  you  put  a  lighted  match  to  a  mass  of  powder  the  whole  of  it  will 
explode  and  be  used  up  at  a  single  discharge,  whether  it  be  made 
up  of  a  single  grain  or  be  as  large  as  a  mountain.  You  have  seen, 
however,  that  from  the  muscle  we  can  get  explosion  after  explosion 
of  nearly  equal  strength.  Still  more  than  this  ;  not  only  is  not  all 
of  the  contractile  material  in  the  muscle  used  up  at  each  short- 
ening, but  the  strength  of  the  different  contractions  may  be  varied ; 
in  other  words,  the  energy  produced  in  the  different  explosions 
can  be  regulated  so  that  they  shall  be  of  any  desired  feebleness. 
You  see  plainly  here  on  our  little  switch  signal  that  as  the  electric 
shock  is  weakened  the  disk  moves  in  a  smaller  and  smaller  circuit, 
showing  the  contractions  to  have  become  correspondingly  feeble. 

Now  I  submit  to  you  that  this  is  a  remarkable  engine  whose  fuel 
is  stored  up  in,  and  is  apiece  with,  its  working  gear  ;  and  a  strange 
explosive  substance  the  violence  of  whose  action  can  be  regulated 
at  will.  You  have  before  heard  that  the  smoothness  and  duration 
of  our  own  voluntary  movements  are  due  to  the  fusion-  of  many 
single  momentary  muscular  contractions.  You  can  now  understand 
what  was  not  clear  before,  how  we  can  call  upon  our  hands  to  make 
those  motions  whose  delicacy  and  variety  no  artificial  machine  can 
imitate. 

We  see  then  that  the  muscle  alone  when  cut  out  of  the  body 
is  probably  able  to  reproduce  all  the  movements  which  it  can 
undergo  in  the  body.  But  it  has  appeared  that  the  muscle  at  rest 
always  remains  so  unless  stirred  up  by  something  outside  itself. 
It  is  like  a  steam  engine  with  steam  up  but  throttle  closed,  doing 
no  work,  and  if  no  hand  turned  the  throttle  lever  it  should  remain 


43 

forever  immovable.     How  then  are  all  our  muscles  in  the  various 
parts  of  the  body  .brought  into  action  at  will  ? 

If  you  were  to  dissect  an  animal,  there  should  be  found  a  slender 
white  cord  attached  by  one  end  to  each  muscle  ;  the  cords  from 
different  muscles  are  gathered  together  in  bundles,  and  thus  all 
take  their  course  toward  the  skulf  or  backbone,  and,  running  through 
holes  in  their  thick  bony  walls,  finally  unite  with  either  the  brain 
or  the  spinal  marrow.  These  two  great  nervous  masses,  the  brain 
and  spinal  marrow,  are  united  with  each  other  through  a  hole  in 
the  bottom  of  the  skull.  Together  they  form  the  so-called  central 
nervous  system,  which  is,  as  you  see,  securely  sheltered  from  harm 
by  the  hard  bony  walls  of  the  skull  and  backbone. 

The  white  cords  which  have  been  mentioned  are  the  nerves,  and 
they,  connect  together  the  central  nervous  system  with  the 
muscles  over  the  whole  body.  If  you  cut  in  two  one  of 
these  nerve-trunks  in  the  living  animal,  all  the  muscles  to  which 
those  nerve  fibres  run  will  be  paralyzed  and  the  animal  incapable 
of  moving  them  again.  So  it  seems  clear  that  whatever  stirs 
up  the  muscle  to  activity  in  the  body  must  pass  along  the  nerves, 
though  these  show  no  signs  of  disturbance. 

It  is  easy  to  prove,  in  fact,  that  the  nerves  do  conduct  impulses 
which  cause  the  muscles  to  contract.  For  you  see  that  by  passing 
an  electric  shock  through  the  nerve  which  is  attached  to  our  switch 
signal  muscle  we  can  get  on  the  muscle  all  the  effects  that  came 
out  when  it  was  directly  excited.  In  this  case  we  have  used  only 
the  nerve  going  to  one  muscle ;  but  it  is  evident  that  if  I  excite  a 
large  nerve-trunk  containing  in  one  bundle  fibres  for  many  differ- 
ent muscles,  each  of  these  muscles  shall  be  independently  excited 
so  that  all  shall  be  made  to  contract.  You  see  thrown  upon  the 
screen  the  legs  and  rump  of  a  frog  whose  body  trunk  has  all  been 
cut  away  except  the  nerves  which  connect  the  legs  with  the  spinal 
marrow.  When  the  electric  current  is  applied  to  different  parts  of 
these  nerves  you  observe  that  the  animal,  what  there  is  left  of  him, 
is  thrown  into  remarkable  contortions. 

Without  doubt,  then,  something  descends  the  nerve  and  excites 
the  muscle,  though  we  see  no  more  sign  of  activity  in  the  nerve  it- 
self than  we  do  in  a  telegraph  wire  along  which  a  message  is  pass- 
ing. The  nerve  bears  somewhat  the  same  relation  to  the  muscle  that 
the  fuse  does  to  the  dynamite  charge  used  in  blasting.  The  nerve 
is  set  on  fire,  as  it  were,  at  the  spot  excited,  and  this  chemical 


44 

change  or  burning  passes  down  the  nerve  like  fire  in  a  fuse.  If  I 
tie  a  string  tightly  around  the  nerve,  its  ignitable  substance  is  di- 
vided by  the  string  into  two  parts,  and  it  is  seen  that  the  nervous 
impulse  is  blocked  by  the  string,  for  a  shock  applied  to  the  nerve 
beyond  it  has  no  effect  on  the  muscle,  while  when  the  nerve  is  ex- 
cited between  the  place  tied  and  the  muscle  the  latter  responds  as 
before.  Just  in  the  same  way,  if  you  soak  with  water  a  fuse  at 
a  point  between  the  fired  end  and  the  dynamite,  the  fire  cannot 
get  to  the  charge. 

You  have  seen  that  the  muscle  is  excitable,  and  that  it  is  also 
contractile.  You  have  been  convinced,  perhaps  no  less  surely, 
that  the  nerve  is  excitable,  and  that  it  is  also  conductive.  Now 
the  nerve  is  simply  a  message-carrier,  and  the  muscle  is  simply  a 
worker.  Our  nerve-muscle  cut  out  of  the  body  could  never  move 
or  show  any  signs  of  life  of  itself. 

But  we  not  only  move  at  will,  but  can  regulate  the  strength  and 
duration  of  our  contractions  to  a  wonderful  degree.  Not  only  that, 
but  the  different  muscles  supplied  by  different  nerves  may  be  made 
to  move  together,  or  one  after  the  other,  as  accurately  as  the  parts 
of  a  working  engine. 

We  may  look  on  the  body  as  an  army  of  which  the  muscles  are 
the  soldiers,  and  the  nerves  the  aides-de-camp  who  carry  messages 
to  the  different  divisions.  A  good  soldier  never  moves  until  com- 
manded to  do  so,  and  thus  we  have  them  working  in  the  body 
singly,  or  in  squads,  or  in  brigades  together.  This  activity  of  the 
muscles  goes  on  so  that  each  muscle,  like  the  soldier,  works  not 
independently,  but  in  a  manner  to  help  the  others  to  accomplish 
some  definite  purpose.  What  and  where  is  the  general  whose 
commands  set  this*  army  into  action  ?  In  what  part  of  the  body 
does  this  wonderful  directing  power  reside  ?  You  will  rightly  con- 
clude that  it  is  in  the  central  nervous  system,  the  brain  and  spinal 
marrow,  from  which  we  have  seen  that  the  nerves  arise.  If  you 
were  to  study  the  brain  or  spinal  marrow,  with  the  microscope,  you 
would  find  in  it  great  numbers  of  tiny  bodies  called  nerve  cells, 
some  of  whose  forms  are  shown  in  Fig.  8.  Nerves  on  entering 
the  brain  and  marrow  no  doubt  unite  with  these  nerve  cells,  and 
the  various  cells  are  connected  together  by  their  long  branches. 
Now  it  is  within  these  nerve  cells,  without  doubt,  that  all  the  plan 
of  action  of  the  body  is  laid  down,  and  from  them  messages  are  sent 
out  along  a  multitude  of  different  paths  to  stir  up  the  muscles  to 


45 


FIG.  8.   Forms  of  nerve  cells,  highly  magnified. 

accomplish  some  purpose.  They  are  the  generals  whose  com- 
mands the  army  of  muscles  obeys.  As  the  nerve  cells  are  so  small 
and  crowded  together  it  is  impossible  to  excite  them  one  by  one, 
and  so  find  out  what  their  special  activities  are,  as  can  be  done  in 
the  case  of  single  nerves.  But  it  is  easy  to  show  that  they  act  in  a 
special  way.  When  I  cut  or  shock  a  nerve  once,  the  muscle  sup- 
plied by  it  contracts  but  once,  and  the  number  and  strength  of  con- 
tractions can  be  regulated  at  will.  But  if  I  cut  with  the  scissors 
through  the  back  of  this  headless  frog,  and  so  mangle  and  excite 
its  spinal  marrow,  you  will  see  the  contraction  that  succeeds  is  long 
continued,  involving  many  muscles,  showing  that  though  the  outer 
disturbance  has  ceased,  the  nerve  centres  are  still  in  a  state  of  ex- 
citement, and  are  sending  out  impulses  which  stir  up  the  muscles. 
Pretty  much  the  same  sort  of  activity  you  have  seen  in  a  chicken 
which  jumps  around  for  a  long  time  after  its  head  has  been  cut  off. 
We  have  traced  now  all  the  movements  of  the  body  up  to  the 
central  nervous  system,  and  can  feel  pretty  sure  that  it  is  the  nerve 
cell  which  sends  out  all  the  messages  that  the  muscles  obey.  But 
these  nerve  cells  are  shut  away  in  a  bony  prison,  safely  removed 
from  the  chance  of  accident.  If  these  cells  are  the  regulators  of 


46 

the  bodily  machine,  how  is  it  that  they  come  to  know  of  outer 
danger  in  order  that  they  may  command  the  muscles  to  prepare  to 
meet  it  ?  How  do  they  know  when  it  is  cold  or  wet,  light  or  dark, 
that  they  may  tell  the  body  to  change  its  clothing  or  to  go  to  bed  ? 
In  order  to  explain  this,  I  shall  have  to  describe  another  set  of 
nerves  that  arise  in  the  spinal  marrow  and  brain,  but  instead  of 
going  to  muscles,  go  to  terminate  in  parts  of  the  body  which  come 
into  contact  with  the  outer  world.  These  nerves  are  just  like  the 
ones  we  have  became  acquainted  with,  except  that  they  conduct 
nervous  impulses  to  the  nerve  cell  instead  of  from  it.  They  are 
called  sensory  nerves,  because  they  lead  from  sense  organs.  For 
example,  the  eye  contains  sense  organs  that  are  excited  by  light, 
the  ear  by  sound,  the  skin  by  heat  and  touch,  the  tongue  by  taste. 
So  tfyat  you  see  if  there  be  a  sound  in  the  air  the  ear  nerve  is  ex- 
cited, and  its  activity  is  transmitted  to  the  brain ;  and  the  brain 
cell,  by  a  faculty  which  we  cannot  in  the  least  understand,  may 
act  on  the  information  so  conveyed  to  it,  and  cause  the  whole  form 
and  position  of  the  body  to  be  changed,  or  the  cell  may  compare  that 
information  with  messages  from  other  sources,  as  the  eye  or  skin, 
and  allow  the  body  to  remain  quietly  at  rest.  Thus,  if  a  man 
walking  in  the  grass  of  a  rattlesnake  region  hears  a  loud  whir-r,  he 
feels  uncomfortable,  and  has- a  decided  impulse  to  spring  back  ;  but 
if  he  looks  and  finds  the  noise  is  only  made  by  a  locust,  the  sen- 
sation derived  from  the  eye  is  compared  in  the  brain  cell  with 
that  coming  from  the  ear,  and  all  alarm  vanishes. 

Some  sort  of  relation  between  sense  organ  and  nerve  centre  as 
that  represented  in  Fig.  9,  is  supposed  to  exist  in  the  body. 

Here  is  a  frog  whose  head  has  been  cut  off.  The  creature  remains 
perfectly  motionless,  and  would  forever  remain  so  if  undisturbed. 
But  when  a  piece  of  paper  which  has  been  dipped  into  weak  acid 
is  put  upon  its  flank,  you  see  that  violent  efforts  are  made  to  wipe 
it  off  with  the  feet.  Now  suppose  I  run  a  wire  down  through  the 
spinal  marrow  and  break  it  up ;  after  some  convulsive  movements, 
the  frog  becomes  perfectly  quiet.  Now  apply  the  acid  and  the 
frog  makes  not  the  slightest  motion.  What  has  happened  ?  The 
skin,  nerves  and  muscles  have  not  been  injured  in  the  least ;  they 
are  still  alive.  The  skin  is  still  excited  by  the  acid,  and  sends  up 
its  messages  toward  the  marrow ;  but  the  nerve  cells  there  have 
been  destroyed,  so  there  is  no  authority  that  can  receive  or  act  on 
information  received. 


OF 


47 

The  living  body  has  been  well  compared  to  the  system  of  gov- 
ernment in  a  country.  The  brain  and  spinal  marrow  are  the 
central  offices  at  the  capital.  The  sensory  nerves  are  the  tele- 
graph wires  connecting  the  capital  with  lookout  stations  all  along 
the  coast  and  frontier,  which  stations  represent  the  sense  organs, 
the  eye,  the  ear,  the  skin,  etc.  Information  of  a  storm  or  of  an 
invasion  by  the  enemy  is  received  at  one  of  these  stations,  and 
the  message  is  telegraphed  to  the  capital,  and  here  that  tele- 
gram is  compared  with  others  constantly  arriving  from  all  over 
the  country.  It  is  then  decided  by  the  executive  what  must  be 
done,  and  so  messages  may  be  sent  out  ordering  this  or  that  col- 
lection of  troops — which,  in  the  body,  are  the  muscles — to  go  and 
do  this  or  that,  the  commands  being^always  intended  to  accomplish 
the  greatest  good  for  the  whole  organism. 


Muscle 


FIG.  9.    Illustrating  the  manner  in  which  the  sense  organ,  nerve  fibre,  nerve  cell 
and  muscle  are  connected  together  in  the  body. 


III. 

ON  FERMENTATION. 


ON  FERMENTATION 


By  W.  T.  SEDGWICK,  PH.  D. 

Associate  in  Biology,  Johns  Hopkins  University. 


I  hesitated  a  long  time  before  finally  deciding  to  speak  to-night 
on  fermentation,  for  fermentation  is  caused  by  such  little  things, 
and  by  things  which  look  so  much  alike,  that  I  cannot  show  you 
many  pictures,  nor  give  you  many  experiments. 

Twenty  years  ago  fermentation  was  not  thought  to  be  a  very 
important  subject,  and  at  that  time  perhaps  it  would  not  have  been 
wise  to  give  a  public  lecture  upon  it,  for  the  little  that  was  known 
would  not  have  been  of  special  interest  to  you  and  me. 

About  1860  however,  while  we,  in  this  country,  were  spoiling 
for  a  fight  and  were  getting  ready  as  fast  as  ever  we  could  to  hew 
each  other  into  pieces ;  while  we  were  racking  our  brains  to  invent 
deadly  guns  and  machines  for  destroying  human  life,  some  of  the 
best  scientific  men  of  Europe  were  patiently  studying  fermentation, 
and  learning  how  to  save  human  life.  While  we  were  passing 
through  a  bloody  war,  they  laid  the  masonry  and  built  the  bridges 
over  which  we  now  walk  almost  boldly  into  the  mysterious  regions 
of  fermentation,  putrefaction,  disease  and  death. 

We  all  know  very  well  how  the  introduction  of  the  telegraph 
and  the  steam-engine  has  laid  open  vast  fields  for  work,  and  has 
brought  face  to-  face  nations  which  before  were  almost  total 
strangers ;  and  I  hope  to  show  you  to-night  that  in  much  the  same 
way  the  introduction  of  a  new  theory  of  fermentation  about  twenty 
years  ago  has  gradually  opened  up  to  scientific  men  a  new  country 
peopled  with  strange  things,  and  has  given  us  a  clue  to  many  mys- 
terious problems  of  life  and  death. 

To-day  we  know  why  yeast  is  useful  to  the  housewife  and  to  1  he 
brewer  ;  why  sweet  liquids  get  sour  if  we  leave  them  in  the  warm 
air ;  why  canned  fruits  spoil,  after  the  can  has  once  been  opened, 


52 

unless  quickly  eaten  up  ;  and  why  preserves  are  pretty  sure  to 
keep  if  made  "  pound  for  pound."  Better  yet,  we  are  beginning 
to  know  why  some  diseases  are  contagious,  and  what  causes  relaps- 
ing fever,  splenic  fever,  consumption  and  so  on.  Best  of  all,  we 
know  why  we  vaccinate  for  small-pox,  and  why,  if  well  done, 
vaccination  protects  us  against  that  loathsome  disease  ;  while  we 
have  bright  hopes  that  some  day,  not  so  very  far  off,  we  may  be 
able  to  vaccinate  for  some  other  diseases  as  we  do  for  small-pox, 
and  so  may  save  many  human  lives. 

As  it  is  a  good  plan  to  begin  on  solid  ground,  we  will  take  up 
first  a  common  example  of  fermentation,  the  alcoholic,  or  thai  fer- 
mentation which  gives  rise  to  alcohol  and  carbonic  acid.  Let  us 
recall  something  with  which  we  are  all  familiar,  and  study  the  fer- 
mentation of  the  juice  of  an  apple. 

An  unripe  or  green  apple  is  hard,  sour,  "  puckery,"  and  not 
tempting,  but  as  it  ripens  a  remarkable  change  comes  on.  It  gets 
mellower,  pulpy  and  sweet,  or  pleasantly  acid — very  unlike  its 
hard,  puckery  self  of  a  few  weeks  before.  Now  even  the  sourest 
ripe  apple  contains  sugar,  and  as  sugar  dissolves  easily  in  the 
water  or  juice  of  the  apple,  that  juice  is  often  sweeter  to  the  taste 
than  the  apple  itself.  Sweet  cider  is  nothing  but  apple-juice,  and 
as  it  comes  from  the  press  it  is  a  mawkish,  insipid  fluid,  very  sweet 
and  always  containing  a  great  deal  of  sugar.  It  is  this  sugar 
which  makes  it  sticky  and  sweet,  and  attractive  to  boys  and  insects. 
The  sweet  apple-juice  or  sweet  cider,  as  it  is  now  called,  is  next 
put  into  a  cask,  and  the  plug  or  bung  is  left  out,  so  that  the  air  has 
free  access  to  the  contents  of  the  cask.  By  the  next  day  a  curious 
thing  has  happened  :  at  least  it  would  be  curious  if  we  were  not  so 
familiar  with  it ;  for  curiosity  depends  a  good  deal  upon  novelty. 
The  taste  of  our  apple -juice  has  changed  and  is  less  sweet,  while 
a  peculiar  pungency  or  sharpness  is  beginning  to  appear.  More- 
over, on  looking  further  we  see  bubbles  of  gas  coming  off,  and  if 
we  let  a  light  down  into  the  cask  (but  not  into  the  liquid)  it  will  go 
out,  proving  that  the  gas  is  not  air.  Now  this  change  of  the  apple- 
juice  from  a  smooth,  sweet  liquid  to  one  stinging  and  not  sweet, 
is  caused,  we  say,  by  the  fermentation  or  working  Q{  the  apple-juice. 

Is  the  apple-juice  then  prone  to  ferment  or  change  ?  Has  it  a 
tendency  to  go  to  pieces?  Or  has  something  gotten  into  it 
and  done  this  thing  ?  These  questions  bring  us  to  the  very  heart 


53 

of  the  matter,  and  we  must  stop  and  reflect  before  we  answer 
them.  One  at  a  time,  however ;  and  first  let  us  see  what  this 
change  is  which  we  have  noticed. — A  sweet  liquid  (apple-juice)  has 
grown  less  sweet,  is  giving  off  bubbles  of  gas,  and  is  becoming 
very  biting  to  the  taste.  Now  if  the  sugar  be  weighed  before  fer- 
mentation has  set  in,  and  if  this  gas  and  biting  liquid  are  collected 
and  weighed,  they  together  will  be  found  equal  in  weight  to  the 
sugar,  or  very  nearly  so.  And  we  can  prove  by  chemical  analysis 
that  the  gas  is  carbonic  acid  gas,  and  the  stinging  liquid  alcohol. 
While  at  first  the  sugar  was  present  and  there  was  no  alcohol  or 
carbonic  acid,  now  the  conditions  are  reversed.  In  fact  sugar  has 
been  changed  gradually  into  carbonic  acid  gas  and  alcohol,  and  this 
is  alcoholic  fermentation — the  changing  of  sugar  into  alcohol  and 
carbonic  acid  gas.  Now  we  may  ask  is  sugar  prone  to  ferment  ? 
Is  it  always  breaking  up  of  its  own  accord  into  these  two  substances, 
or  is  it  broken  up  by  something  outside  of  itself?  We  know  that 
dry  sugar  in  lumps  or  grains  keeps  well  enough.  Hence  it  would 
seem  that  the  sugar  is  sufficiently  firm,  and  is  not,  as  might  be  sup- 
posed, always  tumbling  over  and  breaking  up  into  alcohol  and 
carbonic  acid. 

If,  however,  we  dissolve  some  sugar  in  water  and  leave  it  in  the 
air,  the  sweet  liquid  very  soon  sours.  Perhaps  dissolved  sugar  is 
more  unsteady  then,  and  the  water  breaks  it  up.  But  this  cannot 
be,  for  we  all  know  that  sweet  apple-juice,  so  long  as  it  is  inside 
the  apple,  never  ferments  ;  and  we  know,  too,  that  canned  fruits  and 
preserves  have  much  water  and  sugar  in  them,  yet  they  never  fer- 
ment if  well  prepared  and  kept  closed,  though  they  do  so  very  soon 
if  opened.  Thus  it  is  clear  that  sugar  is  not  prone  to  break  up  of  its 
own  accord,  and  that  mere  water  does  not  make  it  sour  or  "work." 
We  have  not  yet  looked  far  enough.  If  it  is  true  that  sugar  does 
not  of  itself  split  up  into  alcohol  and  carbonic  acid  gas,  it  must  be 
broken  up  by  something  external  to  itself,  somewhat  as  a  block  may 
be  split  into  chips  by  an  axe ;  and  perhaps  a  microscope  might 
show  us  something  in  cider — some  axe — which  is  capable  of  so 
splitting  up  sugar. 

If  we  put  a  small  drop  of  "  working  "  cider  under  a  powerful 
microscope  we  find  in  it  a  good  deal  of  yeast ;  and  we  know  very 
well,  on  thinking  it  over,  that  yeast  turns  sweet  flour  into  sour  dough, 
and  changes  sweet  barley-juice  into  foaming  alcoholic  beer;  so  that 


54 

we  must  ask  at  once,  What  is  yeast  ?  Does  it  split  up  sugar  ?  If 
so,  how  could  it  have  gotten  into  the  cider  ?  And  is  yeast  the 
cause  of  that  queer  splitting  up  of  the  sugar  of  the  apple-juice 
into  alcohol  and  carbonic  acid  gas  which  we  have  noticed  and 
have  called  alcoholic  fermentation  ? 

First,  What  is  yeast?  We  know  that  baker's  yeast  is  a  milky- 
looking  liquid  with  a  muddy  sediment  at  the  bottom ;  and  200 
years  ago  nobody  knew  any  more  than  that  about  it.  About  that 
time  however  (1680),  a  bright  Dutchman  named  Leeuwenhoek, 
a  maker  of  fine  instruments,  made  a  microscope  which  was  better 
than  any  which  had  been  used  before,  and  of  course  he  looked 
at  almost  everything.  He  looked  at  blood  which  till  then  had 
been  supposed  to  be  a  red  liquid,  and  found  that  it  was  really  a 
colorless  liquid  in  which  red  bodies  were  floating  ;  very  much  as 
these  cranberries  float  in  the  water  of  this  big  tube  which  I  hold 
in  my  hand. 

[A  tall  measuring  glass  having  a  bore  of  about  two  inches,  and 
partly  filled  with  water  and  cranberries,  was  so  held  before  the 
audience  as  to  make  the  mass  flow  from  one  end  to  the  other,  and 
produce  a  tolerably  red  mixture  which,  on  standing,  separated 
into  a  red  and  a  colorless  layer.] 

He  also  looked  at  putrid  water,  and  found  what  he  took  to  be 
animals;  very  minute,  wriggling,  worm -like  things.  Finally,  he 
turned  his  glass  upon  yeast,  and  found  that  even  the  liquid  por- 
tion was  no  more  a  mere  liquid  than  the  blood,  but  was  really  a 
colorless  fluid  filled  with  milky-looking  grains ;  very  much  as  if  I 
had  had  small  white  beans  instead  of  cranberries  in  that  tall  tube 
with  the  water. 

Leeuwenhoek  did  not  know  what  these  grains  were ;  but  a  cen- 
tury later,  about  the  time  when  George  Washington  was  our  Pre- 
sident, an  Italian  named  Fabroni  said  he  believed  them  to  be 
alive ;  in  fact  they  seemed  to  him  half  vegetable  and  half  animal, 
or  vegeto-animal  in  their  nature.  Fifty  years  more  went  by,  and 
better  microscopes  had  been  made  when,  in  1837  (about  the  time 
Van  Buren  succeeded  Jackson  as  President),  a  Frenchman,  Cag- 
niard  de  la  Tour  by  name,  went  to  work  upon  these  grains,  and 
found  them  budding  and  growing !  He  at  once  said  that  they  were 
living  plants,  and  many  people  began  working  upon  this  curious 
microscopic  vegetable  ;  till  to-day,  with  yet  better  microscopes,  we 


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56 

know  beyond  question  that  yeast  is  a  liquid  swarming  with  my- 
riads of  curious  little  plants,  all  much  alike,  yet  of  varying  sizes 
and  shapes.  [A  large  diagram  hanging  behind  the  speaker  was 
referred  to,  and  single  cells,  chains  of  cells,  and  budding  colonies 
were  pointed  out.]  (See  Figures  i  and  2.) 

Having  discovered  that  yeast  is  a  little  plant  floating  in  a  liquid > 
we  are  now  ready  for  our  second  question :  Can  yeast  split  up 
sugar  into  alcohol  and  carbonic  acid  gas  f  In  order  to  waste  no 
time,  I  have  prepared  an  experiment  by  which  I  can  answer  that 
question  very  quickly  here  before  your  eyes,  and  can  prove  what 
I  say. 

[A  large  flask  of  actively  fermenting  sugar  solution  previously 
charged  with  yeast  stood  on  the  left  of  the  speaker,  and  from  it  a 
bent  tube  led  off  and  finally  down  into  a  vessel  of  pure  water. 
From  the  end  of  the  tube  beneath  the  surface  of  the  water,  bubbles  of 
gas  could  be  seen  escaping  and  rising  to  the  surface.  On  his  right 
was  a  glass  retort  resting  upon  a  copper  water-bath  heated  by  a 
spirit-lamp.] 

In  this  large  bottle  or  flask  I  put  yesterday  a  rather  strong  solu- 
tion of  cane-sugar  in  water,  then  I  added  some  baker's  yeast,  and 
set  the  flask  aside  in  a  warm  place.  To-day  bubbles  of  gas 
were  coming  off,  and  I  have  attached  this  bent  glass  tube  so  that 
the  gas  in  order  to  escape  has  now  to  bubble  through  the  pure 
water  which  you  see.  Let  us  return  for  a  moment  to  the  apple- 
juice.  That,  too,  was  sugary  at  first,  but  by  the  next  day  was  giving 
off  bubbles  of  gas,  and  we  found  by  our  microscope  that  there  was 
yeast  in  the  cider  (though  we  did  not,  as  we  did  in  this  case,  put  it 
there).  We  know  that  in  the  sweet  apple-juice  the  sugar  particles 
are  somehow  divided  into  bits  of  carbonic  acid  gas,  for  one  thing, 
and  alcohol  for  another.  Moreover  we  suspect  that  yeast  has  done 
the  mischief,  and  we  have  therefore  set  a  trap  for  the  yeast,  have 
given  it  a  supply  of  sugar,  and  are  going  to  see  if  carbonic  acid  gas 
and  alcohol  are  given  off. 

If  they  are  we  must  charge  the  fermentation  of  apple-juice 
to  yeast,  and  then  will  be  the  time  to  ask  where  the  yeast  came 
from.  Here  is  the  yeast  perhaps  already  in  the  trap,  for  a  gas  of 
some  kind  is  certainly  coming  off.  Now  if  I  let  a  lighted  candle 
into  this  vessel  (but  not  into  the  water),  I  shall  be  doing  just  what 
we  did  with  the  cider  cask.  In  that  case  the  flame  was  extinguished* 


57 

How  will  it  be  now  ? — As  you  see,  the  flame  flickers  and  goes  out. 
But  let  us  try  another  test.  Carbonic  acid  gas  will  dissolve  in  water 
very  easily ;  hence  if  this  gas  is  really  carbonic  acid  gas,  the  water 
must  hold  a  good  deal  of  it  in  solution,  for  it  has  had  the  gas  bubbling 
through  it  for  some  time;  and  if  to  the  colorless  water  I  add  this 
colorless  liquid,  known  to  chemists  as  barium  hydrate, 'we  shall 
know  at  once  if  that  gas  has  been  dissolved,  for  if  it  has  we  shall 

see  a  heavy  white  cloud  in  the  water You  see  the  cloud ; 

and  so  we  have  two  proofs  that  carbonic  acid  gas  is  really  given 
off  from  sugar  under  the  activity  of  yeast.  But  you  will  ask, 
Is  alcohol  also  given  off?  Let  us  see. — In  this  retort  was  placed, 
before  the  lecture,  a  lot  of  the  liquid  remaining  from  just  such 
a  fermentation  as  is  now  going  on  in  that  flask  from  which  car- 
bonic acid  is  coming  off.  In  other  words,  the  residue  of  a  sugar 
solution  which  had  been  fermented  by  yeast  and  from  which 
many  volumes  of  carbonic  acid  gas  had  escaped  (as  you  see  it 
escaping  now  from  the  big  flask)  was  put  into  this  retort.  Now 
the  retort  is  a  little  still,  and  if  any  alcohol  is  in  that  residue  it  will 
be  distilled  over  into  the  tube  of  the  retort,  and  then  cooled  and 
condensed  so  as  to  fall  in  drops  from  the  open  end.  Even  while  I 
have  been  speaking  you  have  perhaps  seen  it  dropping,  and  here 
in  this  vessel,  into  which  the  drops  have  fallen,  is  quite  a  quantity 
of  it. 

I  must  now  prove  to  you  that  it  is  really  alcohol,  which  I  will  do 
by  burning  it.  That  bright  blue  flame,  brilliant  and  hot,  is  proof 
enough  that  alcohol  as  well  as  carbonic  acid  gas  is  given  off  when 
yeast  acts  upon  sugar  dissolved  in  water.  Hence  we  are  justified 
in  believing  that  yeast  also  causes  the  sugar  in  apple-juice  to  split 
up  into  alcohol  and  carbonic  acid  gas,  but  we  cannot  be  absolutely 
sure  till  we  make  one  more  experiment. 

If  we  can  remove  the  yeast  or  kill  it  without  changing  the  sugary 
liquid,  then  you  must  admit  that  we  shall  see  certainly  whether 
or  not  yeast  really  makes  this  curious  change  which  we  call  fermen- 
tation. For  if  that  liquid  will  "keep"  in  the  absence  of  living 
yeast,  and  will  always  ferment  when  living  yeast  is  in  it,  then  yeast 
must  be  the  axe  which  splits  it — the  \x\\eferment.  Now  if  we  boil 
yeast  we  always  kill  it ;  but  if  we  boil  sugar  solution  or  sweet  cider, 
or  fruit  which  we  wish  to  preserve,  we  do  not  harm  or  alter  the 
sugar.  Therefore  if  we  boil  sugar  solution  or  sweet  cider  and  seal 


58 

it  while  still  hot  we  shall  have  a  capital  chance  to  see  if  yeast  is  the 
ferment,  for  all  the  yeast  will  be  dead  and  yet  the  sugar  will  be 
there. — You  know  that  cider  or  sugary  fruit  prepared  in  that  way 
and  kept  sealed  never  ferments.  Hence  yeast  must  be  the  axe 
that  splits  the  sugar.  If  any  one  still  thinks  that  the  heating  has 
changed  the  sweet  juice  so  that  it  will  not  ferment,  let  him  open  a 
jar  of  canned  apple-juice  or  fruit,  and  in  two  days  it  will  be  swarm- 
ing with  minute  living  plants, — will  be  fermenting,  and  the  sugar 
will  quickly  be  split  up  into  other  things. 

Let  us  now  pause  and  see  what  we  have  learned  up  to  this  time 
by  our  study. 

We  know  from  observation  and  experience  that  sweet  apple-juice 
contains  sugar,  and  when  fermentation  sets  in  that  it  loses  the  sugar 
and  gets  in  its  place  alcohol  and  carbonic  acid  gas.  The  chemist 
tells  us  that  the  sugar  is  a  complex  body,  and  that  it  is  somehow 
broken  up  into  these  other  products.  Our  experience  teaches  us 
that  it  does  not  of  itself  fall  to  pieces  any  more  than  a  silver  dollar 
of  itself  falls  into  two  halves ;  we  therefore  look  about  us  to  see 
what  has  split  the  sugar,  and  the  microscope  shows  us  yeast  (among 
other  things)  in  the  fermenting  fluid.  Remembering  that  yeast 
often  makes  sweet  things  sour,  we  suspect  that  yeast  may  be  the 
ferment — the  axe  which  has  split  the  sugar,  or  the  agent  which  has 
changed  the  silver  dollar  into  two  halves.  We  then  set  a  trap  for 
it  by  giving  to  some  active  yeast  a  supply  of  sugar  ;  and,  sure 
enough,  instead  of  the  sugar  we  found  by-and-by  a  quantity  of 
alcohol  and  carbonic  acid  gas  !  Feeling  now  almost  certain  that 
the  yeast  is  the  ferment,  we  kill  it  without  altering  the  liquid  and 
find  that  the  sugar  never  ferments  so  long  as  we  keep  living  yeast 
away.  Hence  we  become  absolutely  sure  that  yeast  has  broken 
up  the  sugar  and  changed  it  into  alcohol  and  carbonic-acid  gas. 
This  interesting  change  we  call  alcoholic  fermentation,  the  thing 
{yeast)  which  produces  fermentation  being  called  a  ferment. 

Yeast,  then,  is  a  ferment,  and  we  must  study  it  more  closely  to 

,  see  what  it  is  and  how  it  works.     We  have  learned  that  it  contains 

a  growing,  budding  plant  floating  in  a  liquid.     Is  the  liquid  the 

essential  part  of  the  ferment,  or  is  the  plant  the  true  ferment,  or  are 

both  liquid  and  plant  requisite  to  cause  fermentation  ? 

A  very  distinguished  German  professor  named  Helmholtz  set- 
tled these  questions  in  a  way  which  you  will  easily  under- 
stand. If  I  were  to  walk  with  perfectly  water-tight  leather 


59 

boots  in  very  wet  sand,  even  though  there  were  no  holes  in  the 
boots,  some  moisture  would  come  through  and  dampen  my 
feet ;  it  would  come  through  invisible  pores  in  the  leather — pores 
too  small  to  admit  sand,  but  big  enough  to  let  in  minute  par- 
ticles of  water.  Or,  if  I  pour  water  upon  the  earth  in  an  un- 
glazed  earthen  flower-pot,  the  water  may  "soak"  through  and 
stand  on  the  outside,  though  the  dirt  will  not.  Helmholtz  divided 
a  vessel  into  two  parts  by  a  partition  of  a  thin,  porous  mem- 
brane, like  leather  ;  and  on  one  side  he  put  a  quantity  of  yeast, 
which  was  like  the  wet  sand  ;  the  yeast-plants  being  the  grains  and 
the  liquid  portion  of  yeast  the  water  of  the  sand.  On  the  other  side 
of  the  membrane  he  put  sugar  solution. 

Here  then  was  a  test:  the  yeast  liquid  could. go  through  the 
membrane  and  act,  if  it  chose,  upon  the  sugar ;  while  the  yeast 
plants  could  not  go  through.  Therefore,  if  the  liquid  fermented, 
it  would  prove  that  the  yeast  plants  were  not  necessary  to  cause 
fermentation.  In  point  of  fact  it  did  not  ferment;  hence  we  know 
that  it  is  the  yeast  plant  which  causes  fermentation,  and  that  the 
liquid  portion  of  yeast  is  not  able  to  produce  fermentation. 

How  does  the  yeast  plant  cause  fermentation  ?  How  does  it 
split  up  sugar  f 

These  questions  take  us  into  regions  beyond  the  reach  of  the 
keenest  eye  aided  by  the  most  powerful  microscope.  The  yeast 
plants  and  the  particles  of  sugar  are  so  small  that  we  cannot  see  how 
the  plant  tears  the  sugar  into  pieces.  Chemistry  has,  however, 
taught  us  that  sugar  is  a  complex  thing,  even  when  its  particles  are 
too  small  for  our  eyes  to  grasp,  and  that  a  little  particle  of  sugar 
is  just  as  complex  in  its  real  nature  as  a  big  one. 

Several  theories  as  to  the  way  in  which  yeast  works  have  been 
brought  forward,  but  I  shall  give  you  but  two  of  them.  Liebig, 
the  celebrated  chemist,  believed,  even  till  his  death  some  ten 
years  ago,  that  sugar  particles  are  rather  topheavy  and  un- 
steady— easily  broken  up  into  alcohol  and  carbonic  acid.  He  be- 
lieved that  living  yeast  is  always  in  an  active  state,  its  particles  in 
rapid  motion ;  now,  the  sugar  being  dissolved,  is  on  all  sides  in 
contact  with  the  yeast,  and  is,  therefore,  constantly  receiving  blows 
and  shocks  from  the  whirling  particles  of  the  yeast  vegetables. 
Hence  it  is  upset,  it  breaks  into  two  simpler  things,  and  the  car- 
bonic acid  gas  goes  off  in  bubbles,  while  the  liquid  alcohol  re- 
mains. This  theory  was  very  ingenious,  and  being  held  by  a 


6o 

chemist  so  distinguished,  was  not  easily  overturned.  But  there 
was  one  test  which  finally  overthrew  it.  Liebig's  theory  required 
that  all  of  the  sugar  should  be  split  up  into  simpler  things  ;  and  for  a 
long  time  it  was  believed  that  it  did,  all  of  it,  split  to  alcohol  and 
carbonic  acid,  as  I  split  this  "  card  "  of  biscuit. 

[A  baker's  card  of  biscuit  was  shown,  and  split  into  two  unequal 
parts  by  the  speaker.] 

About  1860,  however,  a  now  distinguished  Frenchman,  Pas- 
teur— of  whom  you  may  never  have  heard,  but  whose  name  your 
children  may  some  day  reverence — made  very  careful  analyses 
and  found  that  the  sugar  is  not  divided  in  that  way,  but  that 
about  four  or  five  per  cent,  of  it  becomes  glycerine,  succinic  acid, 
etc.,  and  that  a  still  smaller  portion  cannot  be  found.  It  was  as 
if  I  should  break  this  card,  having,  say  one  hundred  biscuits  in  it, 
into  two  big  parts — together  making  up  ninety-five,  and  standing 
for  the  alcohol  and  carbonic  acid — and  four  or  five  single  biscuits, 
equal  to  the  four  or  five  per  cent,  of  glycerine,  and  so  on,  and 
should  leave  one  biscuit  out  of  sight,  or  should  eat  it  up. 

Now,  the  question  arose,  what  becomes  of  the  lost  one  per  cent. 
— the  missing  biscuit?  Pasteur  says  that  that  is  devoured  by  the 
yeast  as  a  kind  of  toll  or  reward  for  its  labor  in  splitting  up  the 
sugar.  It  is  easy  to  see  that  the  yeast  has  flourished,  has  increased 
in  quantity,  and  we  believe  it  is  on  these  missing  biscuits  that  it  has 
grown.  He  shows  that  sugar  is  not  easily  upset,  and  does  not 
believe  that  yeast  merely  hits  it,  whereupon  it  straightway  falls  to 
pieces,  but  that  the  living  yeast  plants  take  out  for  their  own  food  a 
small  bit  of  the  complex  sugar  body,  and  that  it  then  falls  to  pieces 
just  as  a  whole  arch  tumbles  if  you  pull  out  the  keystone. 

We  must  now  leave  yeast  and  alcoholic  fermentation  for  a  time 
and  examine  some  other  kinds  of  fermentation  produced  by  other 
ferments.  When  Leeuwenhoek  looked  at  putrid  water,  as  has 
been  said,  he  found  in  it  wriggling,  worm-like  things  which  he  sup- 
posed were  minute  animals.  As  time  went  on,  others  saw  them  in 
solutions  which  were  decaying  or  putrefying,  and  even  so  late  as 
1850  they  were  commonly  supposed  to  be  animals — one  great 
microscopist,  Ehrenberg,  having  in  1838  actually  believed  that 
they  had  stomachs  and  mouths !  About  1860  a  new  idea  arose, 
and  it  was  found  that  they  were  not  animals  at  all,  but  tiny  plants, 
having  a  peculiar  power  of  motion,  and  many  of  them  furnished 
with  long  hair-like  appendages,  by  which  they  were  driven  through 


6i 

the  water  as  an  ocean  steamer  is  driven  by  its  screw.  They  are  so 
tiny  that  one  writer  believes  that  a  space  the  size  of  a  die  such 
as  is  used  in  backgammon,  would  hold  at  least  six  hundreds  of 
millions  of  them  without  having  them  crowded !  It  requires  a 
very  high-power  microscope  to  see  them  at  all,  and  that  is  the 
reason  why  we  were  so  long  in  finding  out  their  true  nature.  (See 
Figures  3  and  4.) 


Fig.  3.    Ferment-plants  (Spirillum  and  Bacterium)  enormously  magnified,  and  show- 
ing the  locomotive  organs  which  are  threads  called  cilia. 


62 

You  will  recollect  that  it  was  about  1 860  that  these  were  dis- 
covered to  be  plants ;  it  was  not  much  later  that  the  new  theory 
of  fermentation — Pasteur's — came  up  and  received  so  much  sup- 
port ;  so  that  this  idea  at  once  occurred  to  some :  If  yeast  is  a 
plant  and  causes  sugar  to  break  up  for  its  own  purposes — that  is, 
for  food — may  it  not  be  that  these  minute  plants  attack  other  sub- 
stances as  yeast  does  sugar ;  that  they  break  them  up  in  much  the 
same  way ;  and  instead  of  rejecting  alcohol  and  carbonic  acid  as 
unfit  for  food,  they  reject  other  things,  which,  in  some  cases,  have 
a  bad  odor  ?  In  other  words,  may  it  not  be  that  putrefaction  is 
really  a  fermentation — not  an  alcoholic  one,  but  a  bad-smelling  fer- 
mentation,— caused  by  little  plants  really  ferments  like  yeast? 
This  view  is  now  very  generally  accepted,  and  we  believe  that 
putrefaction  and  decay,  instead  of  being  the  token  of  death,  are 
really  the  work  of  myriads  of  little  living  things  whose  food  they 
furnish.  Every  decaying  apple  or  banana,  every  muddy  pool  in 
which  garbage  lies,  every  damp,  moist,  bad-smelling  spot  in  our 
homes,  is  probably  swarming  with  these  scavengers.  But  what 
happens  when  the  pools  dry  up  and  when  food  is  scarce  ?  A  very 
important  thing  happens.  The  plants  dry  up  too,  and  many  of 
them  die,  for  they  need  moisture — and  dread  sunshine  and  dryness. 
Some  of  them,  however,  ripen  a  kind  of  seed  called  "germs"  or 
"  spores"  and  these  are  very  light  indeed.  They  are  swept  about 
by  the  wind,  and  dust  is  usually  full  of  them.  Untold  millions  are 
almost  constantly  in  the  air,  and  it  is  these  seeds  which  infect 
canned  fruits.  If  canned  fruits  be  opened  in  air  strained  through 
cotton  (which  will  keep  back  these  spores  and  not  allow  them  to 
pass),  or  if  the  air  in  any  way  be  robbed  of  them  and  so  be  made 
free  from  germs,  then  canned  fruits  may  be  opened  boldly  and  will 
never  ferment.  Purest  mountain  air  is  also  very  free  from  them, 
and  hence  its  value  for  invalids. 

Some  kinds  of  yeast  have  spores  floating  in  the  air,  and  these  are 
the  things  which  made  our  sweet  apple-juice  ferment.  The  cask  was 
"  exposed  "  to  the  germs  in  the  air.  Yeast,  however,  is  limited  in  its 
food.  It  has  but  a  sweet  tooth,  and  lives  usually  upon  sugar,  reject- 
ing in  a  manner  worthy  of  imitation  the  tempting  alcohol  and  car- 
bonic acid.  That  alcohol  is  tempting  can  be  shown  by  a  return  to 
our  cask ;  for  so  soon  as  the  yeast  has  done  its  work  and  has  con- 
verted all  the  sugar  into  alcohol  and  carbonic  acid  gas,  it  falls  to  the 


Fig.  4.  Various  examples  of  microscopic  plants,  some  of  which  produce  putre-* 
faction.  Those  on  the  right  near  the  bottom  show  at  either  end  the  hair-like  appen- 
dage of  locomotion.  All  are  greatly  magnified. 


64 

bottom  of  the  cask  and  a  new  ferment  attacks  the  liquid.  This  is 
the  vinegar  ferment,  and  it  shortly  converts  the  alcohol  into  acetic 
acid,  and  changes  "  hard  "  cider  into  vinegar.  (See  Figure  5.) 


Fig.  5.  The  cells  on  the  left  are  those  of  a  kind  of  yeast  found  in  the  fermenta- 
tion of  wine.  On  the  rigrht  are  flgrured  some  of  the  minute  cells  of  the  vinegar 
ferment  plant.  They  form  chains  which  are  best  described  as  necklace-form. 

Let  us  now  look  at  the  more  practical  side  of  fermentations. 

Bread-making. — In  making  "leavened"  bread  the  ferment  yeast 
is  often  used  to  render  it  "  light."  It  does  this  by  acting,  as  in  other 
cases,  upon  the  sugar  which  is  present  in  the  ripe  grain  or  flour,  and 
changing  it  into  alcohol,  carbonic  acid  gas,  and  some  other  things 
mentioned  above.  The  yeast  having  sugar  at  nearly  every  point, 
.makes  little  bubbles  of  gas  wherever  it  is.  If  it  is  allowed  to  convert 
all  the  sugar  the  bread  becomes  sour.  In  baking,  the  minute  bubbles 
of  carbonic  acid  are  swollen  by  the  heat  and  the  bread  becomes  even 


65 

lighter  than  the  dough.  The  alcohol  is  evaporated  into  the  air  of 
the  oven  and  lost.  In  bread-making,  then,  the  carbonic  acid  gas 
is  wanted,  and  yeast  is  used  to  furnish  it ;  but  that  yeast  is  speedily 
baked  with  the  bread  and  can  never  be  used  again.  Unleavened 
bread  is  dough  baked  without  yeast  or  powders,  and  is  never 
"light." 

Beer-making. — In  making  beer  and  bread  the  sugar  present  in 
ripe  grains  is  used,  while  in  cider-making  and  wine-making  the 
sugar  of  ripe  fruits  is  employed.  In  bread-making  we  use  rye, 
wheat,  etc.,  and  in  beer-making  the  brewer  uses  barley.  He  first 
lets  it  sprout  a  little,  because  the  growing  grain  has  more  sugar  in 
it  than  the  merely  ripe  grain.  But  when  it  has  gotten  very  sugary 
he  roasts  it  and  stops  the  growing ;  the  grain  is  now  called  malt. 
This  sprouted  sugary  grain  having  been  ground  up  and  mixed  with 
water,  hops,  etc.,  is  called  wort,  and  is  ready  for  the  ferment,  yeast ; 
this  having  been  added,  fermentation  (the  change  of  sugar  into 
alcohol  and  carbonic  acid  gas)  begins.  Finally,  as  you  know,  the 
sugar  is  mostly  changed  into  alcohol  and  carbonic  acid,  and  we 
have  essentially,  beer, — a  liquid  pungent  from  the  presence  of 
alcohol  and  full  of  bubbles  of  carbonic  acid  gas. 

Wine-making. — In  using  grape  juice,  which  is  very  sweet,  the 
wine-maker  does  not  add  yeast,  but  its  spores  get  in  from  the  air.  It 
is  true  yeast,  but  is  unlike  the  brewer's  yeast  in  some  respects.  A 
grape  inside  its  skin  seldom  or  never  ferments ;  it  is  hermetically 
sealed  by  its  skin,  but  the  "bloom"  of  the  outside  of  the  grape- 
skin  is  full  of  ferment  germs  awaiting  an  opportunity  to  feed  upon 
and  so  to  ferment  the  sugary  juice  inside.  (See  Fig.  5.) 

Souring  of  milk. — Milk  placed  in  a  warm  room  and  exposed  to 
the  germs  or  spores  in  the  air  speedily  sours.  Now  milk,  too, 
contains  a  kind  of  sugar  which  gives  it  pleasant  sweetness,  and  it  is 
the  change  of  this  sugar  which  makes  it  sour ;  for  instead  of  being 
changed  into  alcohol  and  a  gaseous  acid,  it  is  changed  into  a  liquid 
acid  called  lactic  acid.  This  change,  too,  is  caused  by  a  ferment 
plant,  but  not  by  a  true  yeast.  Why  do  we  set  milk  in  a  cool  place 
or  upon  ice,  to  save  it  ?  Simply  because  in  that  way  we  check 
the  growth  of  the  ferment,  and  growth  of  the  ferment  plants  means 
fermentation.  If  a  geranium  or  a  rose-bush  were  put  upon  ice  or 
in  a  cold  cellar  it  would  not  grow ;  no  more  will  a  ferment-plant ; 
it  does  not  change  its  nature  because  it  is  small.  Why  do  we  scald 


OF  THE 

UNIVERSITY 


66 

milk  or  other  things  about  to  sour  ?  Simply  because  boiling,  as  it 
does  with  yeast,  will  kill  the  various  ferments  and  so  stop  fermenta- 
tion. To  boil  a  geranium  would  kill  it,  and  even  if  new  geranium 
seeds  were  soon  planted  from  the  air  they  would  need  time  to  de- 
velop. Ferments  are  plants  too,  and  their  germs  need  time  to 
develop,  hence  we  can  stop  fermentation  for  a  time,  by  scalding. 
But  the  process  must  be  often  repeated  in  order  to  save  the  milk 
for  a  long  time. 

Preserving  and  Canning. — You  are  familiar  with  both  these 
operations.  In  canning,  the  sweet,  sugary  fruits,  or  the  meats  which 
would  easily  "  spoil,"  are  put  into  cans,  heated  for  a  time,  and 
sealed  up  while  still  hot.  The  heat  kills  the  ferments  present  at 
the  time,  and  the  tight  sealing  keeps  the  spores  of  other  ferments 
out.  Hence  there  are  two  important  steps — heating  and  sealing. 
If  either  is  badly  done  the  operation  is  useless.  The  "  keeping  "  of 
canned  meats  and  sugary  things  proves  that  such  bodies  must  be 
acted  upon  from  without ;  they  never  putrefy  nor  sour  of  their  own 
accord  ;  but  if  the  cans  be  opened  they  spoil  in  a  day  or  two — that 
is,  as  soon  as  the  germs  of  ferments  can  get  in  from  the  air  and 
sprout  and  grow.  The  life  of  the  ferment  means  the  death  and 
destruction  of  the  thing  it  feeds  upon — the  thing  fermented ;  the 
death  or  absence  of  all  ferments  means  the  preservation  of  the  meats 
or  fruits. 

Preserving  is  an  older  method  of  saving  things  which  would 
easily  ferment,  and  is  still  used  for  fruits.  It  depends  for  success 
upon  a  very  simple  fact,  namely,  that  ferments  must  have  water 
in  order  to  grow ;  and  a  good  deal  of  water  too.  They  live  ordin- 
arily only  in  watery  fluids  and  are  themselves  watery.  It  is  as  if  a 
seed  "  fell  upon  dry  ground  "  when  ferment  germs  fall  into  "  pre- 
serves," for  the  syrup,  which  itself  greedily  absorbs  water,  not  only 
fails  to  supply  the  thirsty  yeast,  but  actually  robs  it  of  much  of  the 
water  which"  yeast  always  contains.  Yeast  is  in  this  way  utterly 
paralyzed. 

"Preserves"  are  much  more  sugary  than  watery,  and  though 
the  germs  do  fall  into  them  they  cannot  grow  for  lack  of  water ; 
if,  however,  we  dilute  the  preserves  they  will  swarm  with  ferments. 
Many  a  housewife  has  learned  to  her  sorrow  when  too  late  that  her 
preserves  were  not  "  thick  "  enough,  which  means  they  were  too 
watery ;  too  watery  for  preservation,  but  a  happy  hunting-ground 
for  the  ferments. 


67 

• 

With  jellies  there  are  even  fewer  chances  of  fermentation,  owing 
to  the  necessary  solidity  of  the  fruit  juices. 

Disease -Ferments. — About  1850  a  French  observer  saw  in  the 
blood  of  animals  having  a  certain  fever,  organisms  which  were  very 
small  and  rod-like.  He  did  not  think  very  much  about  them, 
however,  and  it  did  not  occur  to  very  many  that  they  were  really  a 
ferment  till  after  Pasteur  had  written  in  1860,  or  thereabouts. 
From  that  time  a  new  theory  of  contagious  and  infectious  diseases 
has  grown  up,  till  to-day  the  so-called  "  Germ  Theory  "  is  one  of 
the  best  things  we  have  by  which  to  comprehend  disease.  It  is  aston- 
ishing how  much  likeness  there  is  between  fermentation  (say  of 
apple-juice)  and  some  diseases.  For  example,  an  unvaccinated 
person  is  exposed  to  small-pox.  For  a  time  nothing  happens. 
Then  comes  the  fever  and  rise  of  temperature — the  period  of  dis- 
turbance. Next  comes  freedom  from  fever  and  recovery,  or  death. 
So  with  the  cask  of  apple-juice.  It  "is  first  "  exposed  "  to  the  germs 
in  the  air.  Then  comes  a  period  during  which  little  or  nothing 
happens.  This  is  followed  by  active  fermentation — the  sickness 
of  the  apple-juice — and  a  rise  of  temperature  or  its  fever.  Then 
come  rest  and  absence  of  fermentation — the  period  of  recovery. 

In  the  small -pox  the  patient  usually  has  the  disease  but  once, 
very  much  as  the  barrel  of  cider  ferments  but  once. 

The  series  of  events  in  the  two  cases  may  be  put  side  by  side  in 
this  way : 

Disease — Small-pox.  Fermentation — Apple-juice. 

1.  Period  of  exposure.  i.  Period  of  exposure. 

2.  Period  of  repose.  2.  Period  of  repose.                       , 

3.  Sickness  of  patient ;  fever  ;  rise     3.  Working  of  the  apple-juice  ;    rise 

of  temperature.  of  temperature. 

4.  Recovery  or  death.  4.   Cessation  of  the  fermentation. 

5.  Protection  (if  living)  from  another     5.   Protection  from  another  fermenta- 

attack  of  the  same  disease.  tion  by  the  same  ferment. 

By  such  examples  it  is  easy  to  see  how  we  might  suppose  a 
person  suffering  with  small-pox  to  be  really  undergoing  a  fermen- 
tation. "  Exposed "  to  the  disease,  he  receives  into  his  lungs 
spores  or  germs.  These  slowly  develop,  as  in  cider  or  milk,  but 
at  length  bring  him  down ;  they  exhaust  the  food  upon  which  they 
thrive,  and  so  cease  to  behave  as  ferments.  The  principal  objec- 
tion to  this  theory  is  that  it  is  not  yet  proven  in  the  case  of  very 
many  diseases.  In  some,  however,  it  is  proven  beyond  a  doubt, 


68 


Fig.  6.  THE  FERMENT- PiiANT  or  THE  SPLENIC  PEVEB.  At  the  top  and  to  the 
left,  spores  are  seen,  and  on  the  right  they  are  growing:  out  into  long  narrow  rods. 
Half-way  down,  spores  are  seen  forming  within  these  rods  or  tubes,  and  at  the 
bottom  also  may  be  seen  a  similar  process.  (Highly  magnified.) 


69 

and  in  two  of  these,  spleen  fever  and  relapsing  fever,  there  is  no 
doubt  that  we  have  a  true  fermentation  caused  by  plant-ferments. 
Spleen  Fever,  or  Malignant  Pustule. — Although  it  is  not  much 
heard  of  in  this  country,  there  is  a  dangerous  infectious  disease  com- 
mon in  Europe  (especially  in  Russia  and  Germany)  called  splenic 
fever,  or  malignant  pustule.  It  attacks  both  men  and  lower  ani- 
mals, and  has  carried  off  thousands  upon  thousands  of  sheep, 
cattle,  pigs  and  horses,  besides  hundreds  of  human  beings.  Now, 
this  disease  has  been  carefully  studied,  and  it  has  been  proven 
beyond  any  doubt  to  be  really  a  kind  of  fermentation  caused  by 
a  microscopic  plant  called  Bacillus.  This  Bacillus  is  closely 
related  to  well-known  ferments,  and  can  scarcely  be  distinguished 
from  them  except  by  its  behavior.  They  are  harmless,  but  this 
one  is  deadly.  The  figures  show  it,  very  much  magnified,  in 
different  forms  and  stages.  (See  Figures  6  and  7.) 


Fig.  7.  SPLENIC-FEVER  PI^ANTS.  On  the  left  greatly  intertwined  filaments  or 
branches,  within  which  spores  may  be  seen.  On  the  right  straUrhter  rods  lying 
amongst  shrivelled  blood-corpuscles.  (Highly  magnified.) 


7° 

Relapsing  Fever. — This  is  a  peculiar  epidemic  fever  also  com- 
mon in  Germany  and  Russia,  in  which  the  patient  is  seized  by 
a  sharp  fever  which  lasts  about  a  week,  and  then  ends  with  a 
severe  sweating ;  after  the  sweating  the  patient  seems  to  be  get- 
ting better,  when  another  attack  comes  on  and  behaves  like  the 
first ;  again  the  fever  leaves  him  and  again  comes  a  relapse,  till 
finally  recovery  or  death  takes  place.  This  fever,  too,  has  been 
studied,  and  its  ferment  has  been  figured  and  described.  The 
disease  is  apparently  a  true  fermentation,  and  caused  by  a  true 
ferment-plant.  Other  cases  might  be  given,  but  these  must  suffice.* 


Fig.  8.    A  plant-one  of  the  moulds— growing  with  very  little  air.    Observe  espe- 
cially the  long  tubes  ami  compare  with  Fig.  9.    (Moderately  enlarged.) 

*  Within  a  few  weeks  of  the  time  when  this  lecture  was  given,  Robert  Koch,  the  German 
biographer  of  the  ferment  of  splenic  fever,  announced  his  discovery  of  a  disease-ferment  which 
produces  lung-consumption.  This  discovery  has  caused  intense  excitement  wherever  it  is  known, 
and  those  best  competent  to  decide  are  convinced  that  Koch  is  correct,  and  that  some  forms  of 
consumption  are  certainly  produced  by  this  little  plant.  It  is  a  near  relative  of  that  which 
produces  splenic  fever,  but  anything  further  concerning  it  would  be  out  of  place  here. 


7' 

Habits  of  Ferment- Plants. — One  of  the  most  wonderful  and 
extremely  important  things  about  ferments  is  that  they  are  able  to 
change  their  habits  of  life  under  certain  conditions.  Yeast,  for 
example,  behaves  very  differently  according  to  the  food  it  gets. 
Like  some  higher  forms  of  life  it  must  have  food,  but  will  get  it 
where  it  can  get  it  easiest.  If,  however,  it  is  partly  starved  by 


Fig.  9.    The  same  plant  as  shown  in  Fig.  8,  but  growing  with  very  much  less  air. 
Its  starving  condition  has  sufficed  to  change  its  shape.    Compare  Fig.  8. 

(Moderately  enlarged.) 

having  too  little  air,  it  becomes  a  more  powerful  ferment  and  tears 
sugar  to  pieces  much  more  violently.  Now,  if  a  dog  is  well 
used  and  is  given  plenty  of  good  food,  he  will  not  be  so  likely  to 
become  violent  and  dangerous  as  when  he  is  abused  and  gets  little 
or  no  food  and  is  always  half  starved.  It  has  been  found  that  fer- 
ments are,  in  regard  to  their  food,  much  like  the  dog.  If  well  fed 


72 

and  given  air  enough  they  are  usually  harmless,  but  if  starved 
too  much  they  may  become  dangerous.  The  important  point  is, 
\ha\.  ferments  may,  under  certain  circumstances,  change  their  mode 
of  life.  As  a  kind,  harmless  dog  may  by  abuse  and  bad  feeding 
sometimes  be  changed  into  a  miserable,  vicious  cur,  so  a  harmless 
ferment-plant,  when  good  food  and  air  are  taken  from  it,  may 
become  a  deadly  poison  capable  of  producing  disease  and  death. 
Thus  ij:  is  said  that  the  common  blue  mould  which  you  have 
seen  upon  jellies,  jams  and  fruits,  as  well  as  upon  old  boots  and  damp 
walls,  by  bad  treatment  (lack  of  air  and  food)  may  become  a 
dangerous,  poisonous  plant.  On  the  other  hand,  precisely  as  a 
bad  dog  may  sometimes  be  improved  and  made  less  dangerous  by 
kindness  and  good  food.  so«some  dangerous  ferment-plants  may 
change  their  habits  under  good  conditions  and  become  less 
harmful. 


>V 


Pig.  10.    THE  FERMENT- PLANT  OP  CHICKEN  CHOLERA.    On  the  left  greatly,  on  the 
right  less  enlarged. 


73 

Vaccination. — On  the  fact  that  the  habits  of  a  plant-ferment  may 
change  is  based  the  theory  of  vaccination.  Pasteur  has  lately 
proven  that  by  proper  care  the  ferment  of  chicken  cholera  may  be 
made  less  harmful,  and  so  modified  that,  instead  of  killing  the  fowl, 
it  will  merely  sicken  it  and  the  bird  will  finally  recover.  Moreover, 
it  is  a  fact  that  the  tamed  ferment-plants,  though  they  do  not  kill — 
like  the  violent  and  poisonous  ones — do  eat  up,  probably,  the  foods 
upon  which  the  latter  would  live  ;  at  any  rate,  after  a  chicken  has 
had  the  mild,  harmless  cholera,  by  which  it  is  only  sickened  and 
not  killed,  it  cannot  ordinarily  have  the  dangerous  form  of  the 
disease.  Accordingly  Pasteur  vaccinates  chickens,  and  though 
they  are  ill  for  a  time — as  a  man  is  who  has  "  a  bad  arm  " — they 
do  not  often  die,  and  afterwards  they  rarely,  if  ever,  have  the  dis- 
ease again.  In  this  way  many  thousands  of  chickens  have  already 
been  saved.  In  this  way,  too,  sheep  have  been  saved,  and  it  is 
hoped,  as  time  goes  on,  that  the  ferments  of  many  diseases  which 
afHict  mankind  may  be  cultivated  outside  the  body — may  be  tamed 
and  rendered  harmless,  so  that  finally  they  or  their  descendants 
may  be  used  as  weapons  (by  vaccination)  against  the  severe 
forms  of  the  diseases. 

Finally,  you  must  have  seen  that  any  filth,  or  bad  air,  or  decay- 
ing substances  may  become  the  home  of  dangerous  and  even 
deadly  disease-ferments.  And  since  pure  air,  sunshine  and  clean 
homes  are  the  enemies  of  such  things,  they  are  among  our  very 
best  friends.  Dirt,  filth,  decay  and  baol  air  may  change  harmless 
tiny  plants  into  terrible  disease-poisons ;  hence  let  us  see  to  it  that 
our  homes  are  clean  and  pure,  always  full  of  fresh  air  and 
of  sunshine. 


IV. 


ON  SOME  METHODS  OF  LOCOMOTION  IN 
ANIMALS. 


ON  SOME  METHODS  OF  LOCOMOTION  IN 
ANIMALS. 

By  W.  K.  BROOKS,  PH.  D. 

Associate  in  Biology    Johns  Hopkins  University. 


I  was  taught  at  school,  and  I  suppose  that  many  of  my  hearers 
were  also,  that  the  difference  between  plants  and  animals  is  this : 
that  plants  grow,  while  animals  both  grow  and  move.  Times 
change,  and  many  things  which  were  once  thought  to  be  absolutely 
true  are  now  known  to  be  only  partially  true.  There  are  many 
plants  which  are  able  to  move  about  with  great  activity,  and  I  shall 
speak  to  you  soon  of  animals  which  are  as  firmly  rooted  to  one 
spot  as  an  oak  tree.  Still  we  naturally  associate  the  power  of  loco- 
motion with  the  idea  of  an  animal,  and  animals  are,  as  a  rule,  char- 
acterized by  their  ability  to  move  about  at  will. 

I  shall  speak  to  you  this  evening  of  some  of  the  less  familiar 
modes  of  locomotion  in  animals.  We  are  well  acquainted  with  the 
flight  of  insects  and  birds,  the  swimming  of  fishes  and  turtles,  and 
the  climbing,  running  and  walking  of  quadrupeds ;  but  there  are 
many  animals  which  from  their  small  size,  or  because  of  the  places 
where  they  live,  are  less  familiar  to  us,  and  among  these  we  find 
many  contrivances  for  movement  from  place  to  place  which  will, 
I  think,  be  novel  and  interesting  to  y§>u. 

The  first  animal  I  wish  to  speak  of  is  one  which  is  able  to  move 
about  freely,  although  it  is  absolutely  without  moving  organs.  It 
not  only  has  no  limbs,  no  wings,  fins,  arms  or  legs,  but  it  has  no 
bones,  no  muscles,  and  no  nerves.  It  is  a  very  common  animal, 
but  as  it  is  invisible  without  a  microscope,  it  is  a  total  slranger  to 
most  of  us.  It  is  called  by  a  Greek  name,  which  may  be  trans- 
lated the  changeable  animal.  (Fig.  i.) 

If  a  little  of  the  green  film  from  the  bottom  of  a  pond  or  ditch 
be  placed  in  a  watch-crystal  and  carefully  examined  with  a  micro- 


Fig.  1.  The  changeable  animal,  greatly  magnified.     From  Ceidy. 

scope,  it  will  probably  be  found  to  contain  a  few  little  irregu- 
lar, rounded  lumps  of  transparent  jelly.  They  may  be  almost 
perfectly  transparent,  or  they  may  contain  grains  of  sand  and  dirt, 
microscopic  plants,  and  other  foreign  bodies.  These  little  lumps 
are  the  changeable  animals.  For  some  time  after  they  have  been 
handled  they  remain  quiet,  and  no  one  would  suppose  that  they  are 
living  things  ;  but  it  is  only  necessary  to  keep  one  of  them  in  view 
until  it  has  recovered  from  the  shock  produced  by  placing  it  under 
the  microscope,  in  order  to  discover  signs  of  life.  As  soon  as  it  is 
sure  that  the  danger  is  over  it  begins  to  change  its  shape  a  little, 
but  very  slowly.  The  outline  of  the  body  becomes  irregular,  and 


79 

little  rounded  projections  make  their  appearance  around  its  body. 
These  eminences  grow  and  change  slowly ;  so  slowly  that  the  change 
might  easily  be  overlooked;  but  careful  drawings  made  at  short 
intervals  show  that  the  outline  of  the  body  is  varying  continually, 
and  in  a  few  minutes  the  rounded  lump  becomes  transformed  into 
something  like  a  map  of  an  irregular  island,  with  a  notched  and  in- 
dented coast,  deep  bays,  and  long  irregular  peninsulas.  The  out- 
line changes  continually,  bays  filling  up  and  peninsulas  disappear- 
ing, while  others  are  formed  in  new  places.  After  a  time,  when 
the  animal  has  decided  which  way  it  wishes  to  move,  one  of  the 
peninsulas  begins  to  grow  larger  than  the  others.  Careful  ex- 
amination will  show  that  the  substance  of  the  body  is  flowing  in 
slow,  steady  currents  into  this,  and  its  tip  gradually  enlarges,  until 
the  animal  is  divided  into  two  irregular  islands,  connected  by  an 
irregular  isthmus.  Soon  the  new  islancrbecomes  larger  than  the 
old  one;  the  remains ^f  the  latter  then  flow  across  the  isthmus, 
leaving  this  as  a  peninsula.  This  now  flows  into  the  new  body, 
and  the  animal  has  moved  a  step  ;  but  before  this  change  is  com- 
pleted, -another  peninsula  may  grow  out  from  some  other  part  of 
the  body,  so  that  the  animal  may  flow  along  in  several  directions 
at  the  same  time.  If  in  its  travels  any  part  of  the  body  touches 
anything  which  is  fit  for  food,  it  flows  around  it,  as  a  drop  of 
water  would  do,  and  having  got  it  inside  its  body  in  this  way,  it 
digests  it.  If  this  food  is  a  small  animal  with  a  hard  indigestible 
shell,  it  digests  out  the  soft  parts,  and  then  flowing  away,  leaves  the 
shell  behind.  If  it  is  suddenly  startled  by  a  jar,  or  by  the  touch  of 
a  larger  animal,  it  draws  in  all  its  outlying  projections,  and  making 
itself  as  small  and  compact  as  possible,  it  remains  quiet  until  the 
danger  is  past. 

This  is  the  simplest  method  of  motion  in  animals,  and  the 
changeable  animal  is  one  of  the  simplest  living  things  known.  The 
next  method  of  motion  of  which  I  wish  to  speak  is  very  simple, 
but  it  is  performed  by  definite  parts.  It  is  motion  by  what  may 
be  called  swimming  hairs,  and  it  is  most  easily  studied  in  the 
microscopic  animals  known  as  Infusoria.  If  we  make  an  infusion  of 
hay  or  straw,  or  of  dry  moss  and  leaves,  by  putting  a  small  quantity 
into  a  tumbler  of  water,  we  shall  find,  after  it  has  stood  for  a  few 
days  exposed  to  the  air  in  a  warm  place,  that  the  surface  of  the 
water  is  covered  with  a  white  film.  A  fragment  of  this  film,  when 
examined  in  a  drop  of  water  under  the  microscope,  is  found  to  be 


8o 


ils 


made  up  almost  entirely  of  small  transparent  animals,  which  are 
known  as  Infusoria  from  the  fact  that  they  nearly  always  make  their 
appearance  in  organic  infusions  after  they  have 
been  exposed  for  a  short  time  to  the  air.  They 
do  not  flow  along  like  the  changeable  animal, 
but  dart  actively  from  place  to  place.  They 
are  soft  and  transparent,  and  their  flexible 
bodies  change  their  shape  when  they  come  into 
contact  with  each  other  or  with  hard  substances, 
but  each  one  of  them  has  a  definite  form  which 
it  always  assumes  when  other  bodies  do  not 
prevent.  One  of  the  most  common  Infusoria 
is  known,  from  its  shape,  as  the  slipper  animal. 
(Fig.  2.)  It  has  a  long  oval  body,  drawn  out 
to  a  £oint  at  one  end  to  represent  the  toe  of 
the  slipper,  and  rounded  at  the  opposite  end 
or  heel.  On  one  side  there  is  a  depression  like 
the  opening  for  the  foot,  and  at  the  bottom  of 
this  is  the  animal's  mouth. 

The  slipper  animal  glides  about  with  great 
rapidity,  and  changes  its  course  at  will ;  but 
when  it  is  examined  'with  a  low  magnifying 
power,  no  traces  of  locomotor  organs  can  be 
seen.  Its  motions  are  very  puzzling,  for  it 
seems  to  have  in  itself  no  more  means  of  pro- 
pulsion than  an  arrow  has,  and  it  would  cer- 
tainly be  very  puzzling  to  find  an  arrow  turning 
to  the  right  ancf  left,  stopping  and  starting 
again,  and  continuing  in  motion  long  after  it 
had  left  the  bow.  On  more  careful  examina- 
tion we  find  that  the  fine  floating  particles  which 
are  contained  in  the  water  never  come  close  to 
the  animal's  body,  but  that  there  is  a  thin 
belt  of  perfectly  transparent  water  around  its  whole  body.  We 
find,  too,  that  whenever  a  large  particle  of  dirt  approaches  the 
surface  of  the  body  it  is  shot  away,  and  these  facts  seem  to  indi- 
cate that  the  body  is  covered  by  a  locomotor  mechanism  of  some 
kind,  so  small  and  so  active  that  it  eludes  observation.  Finding 
a  specimen  which  has  got  into  a  corner  where  there  is  not  suffi- 
cient water  we  discover  that  this  is  the  case ;  for  as  the  animal  grows 


• 


Fig.  2.  Slipper  ani- 
mal, greatly  magni- 
fied. Copied  from 
H.  J.  Clark. 


weaker,  the  whole  surface  of  the  body  is  seen  to  be  covered  by 
thousands  of  little  transparent  hairs.  These  hairs  lash  the  water 
like  oars,  and  as  their  motion  in  one  direction  is  more  violent  than 
the  motion  in  the  opposite  direction,  they  act  as  oars  to  row  the 
animal  through  the  water.  Around  the  opening  of  the  slipper 
there  is  a  circle  of  somewhat  larger  hairs,  which  are  so  placed  that 
instead  of  moving  the  animal  along,  they  drive  food  into  its  mouth. 

Locomotion  by  swimming  hairs,  or  as  they  are  technically 
called,  by  cilia,  is  not  confined  to  very  simple  and  minute  animals, 
but  it  is  frequently  met  with  in  the  young  of  higher  and  larger 
animals,  even  when  the  full-grown  animal  moves  in  quite  a  differ- 
ent way.  A  full-grown  snail  is  a  crawling  animal,  creeping  over 
the  ground  by  means  of  a  flat,  muscular  foot.  The  newly-hatched 
young  of  many  marine  snails  are  able  to  swim  with  great  activity, 
by  means  of  an  interesting  mechanism  of  swimming  hairs.  When 
the  surface  of  the  ocean  is  skimmed  with  a  fine  net  on  a  calm  even- 
ing, numbers  of  these  young  snails  will  usually  be  captured.  When 
they  are  placed  under  the  microscope  in  a  little  water  they  draw 
back  into  their  shells  and  drop  to  the  bottom,  so  that  examination 
at  first  shows  nothing  except  a  number  of  delicate  and  gracefully 
coiled  spiral  shells,  lying  on  the  bottom  and  apparently  empty. 
After  a  time  a  little  foot  is  protruded  from  the  shell,  and  then  a 
pair  of  feelers  with  eyes  upon  them.  Soon  afterwards  the  animal 
spreads  out  from  the  opening  a  pair  of  broad  but  very  thin  fans  or 
sails,  fringed  with  long,  slender  swimming  hairs.  As  these  lash  the 
water  the  animal  rises  from  the  bottom  and  swims  away.  If  it  is 
disturbed  by  a  gentle  tap  on  the  table,  it  instantly  folds  down  its 
swimming  hairs,  draws  in  and  stows  away  its  sails,  and  drops  to  the 
bottom,  to  lie  there  until  the  supposed  danger  is  past.  (Fig.  3.) 

The  young  oyster  (Fig.  4)  also  swims  actively  by  a  cluster  of 
long  swimming-hairs  which  are  arranged  around  a  thickened  pad 
at  the  anterior  end  <5!"  the  body.  The  swimming  life  of  the  oyster 
is  very  short,  however,  and  it  soon  loses  its  swimming  organ  and 
settles  down  for  life. 

The  young  of  the  starfish  also  swims  by  means  of  swimming 
hairs,  while  the  adult  has  a  complicated  locomotor  apparatus,  which 
is  so  peculiar  that  it  is  well  worth  careful  examination.  Those  of 
you  whose  acquaintance  with  starfishes  extends  no  further  than  the 
dried  specimens  which  are  brought  home  by  visitors  at  the  sea- 
shore, may  be  surprised  to  learn  that  the  animal  has  any  power  of 


82 


Fig.  3.  A  young  marine  Snail,  swimming  by  the  cilia  around  the  free  edge  of  its 
sail ;  greatly  magnified.    Drawn  from  nature  by  W.  K.  Brooks. 


Fig.  4.  A  young  Oyster,  swimming  by  a  tuft  of  swimming  hairs;  greatly  magnified. 
Drawn  from  nature  by  W.  K.  Brooks. 


83 

locomotion,  for  the  dried  specimen  appears  to  be  simply  an  inflexible, 
brittle,  stony  star.  (Fig.  5.)  The  living  animal  is  quite  different; 
the  rays  of  the  star  are  soft  and  can  bend  in  every  direction,  and 
along  the  bottom  of  each  ray  there  are  two  rows  of  long,  slender, 
transparent  feet,  several  hundred  in  each  row.  The  feet  are  tubu- 


Fig.  5.  Lower  surface  of  a  living  Star  Fish,  to  show  the  sucking  feet ;  smaller  than 
life.    Copied  from  A.  Agassiz. 

lar ;  capable  of  considerable  protrusion  and  retraction,  and  each 
one  ends  in  a  little  sucker.  The  foot  is  hollow  and  is  filled  with 
water,  and  its  wall  contains  a  set  of  circular  muscles,  and  also  a  set 
of  longitudinal  muscles.  The  cavity  of  each  foot  communicates, 
through  a  narrow  tube,  with  a  little  muscular  bladder  inside  the 
body,  and  filled  like  the  foot  with  water.  When  walking  the  ani- 


84 

mal  relaxes  the  muscles  of  the  foot,  and  contracting  the  muscles  of 
the  bladder  drives  the  water  out  into  the  foot.  It  then  contracts 
the  circular  muscles  of  the  foot,  and  thus  renders  it  long  and  slen- 
der, and  protrudes  it  until  the  sucker  reaches  and  fastens  upon  the 
surface  over  which  the  animal  is  moving.  The  muscles  of  the 
bladder  and  the  circular  muscles  are  then  relaxed,  and  the  longitu- 
dinal muscles  contracting,  the  water  is  driven  out  of  the  foot  into 
the  bladder,  and  the  foot  is  thus  shortened,  and  the  body  of  the 
animal  is  pulled  forward  to  the  point  of  attachment.  The  bladders 
and  feet  are  supplied  with  water  through  a  complicated  set  of 
tubes  or  pipes,  which  run  to  nearly  every  part  of  the  body. 


Fig.   6.    A   swimming  Jelly   Fish,   slightly  magnified.     Drawn   from  nature  by 

W.  K.  Brooks. 


In  the  jelly-fishes  water  is  employed  as  a  means  of  locomotion 
in  a  different  way.  A  jelly-fish  may  be  compared  to  a  flat  hemi- 
spherical bell  without  a  handle.  The  greater  part  of  the  body  con- 
sists of  a  gelatinous  elastic  body,  or  umbrella,  as  it  is  called,  and 
the  stomach,  mouth  and  other  organs  hang  down  from  the 
centre  of  the  umbrella  like  the  clapper  in  a  bell.  (Fig.  6.)  The 
umbrella  is  thin  near  the  edge,  but  in  the  centre  it  is  thick,  and 


so  elastic  that  it  quickly  recovers  its  shape  after  being  compressed. 
The  mouth  of  the  bell  is  not  entirely  open,  but  is  partially  closed 
by  a  thin,  flat,  horizontal  ring,  the  veil,  which  runs  inwards  around 
its  lower  edge.  The  veil  is  so  thin  that  it  can  be  pushed  in  or 
drawn  out  into  a  short  funnel.  On  the  inner  surface  of  the  um- 
brella are  muscular  fibres,  which  run,  in  circles,  round  the  central 
chamber,  and  when  contracted  expel  the  water  from  under  the 
umbrella,  through  the  opening  of  the  veil.  In  swimming  the 
animal  relaxes  these  muscles,  and  as  the  elasticity  of  the  wall  of 
the  umbrella  opens  it,  the  water  flows  in  through  the  opening  of 
the  veil  and  fills  the  central  chamber.  It  then  violently  contracts 
its  muscles,  and,  forcing  the  water  out  in  a  strong  jet,  drives  its  body 
through  the  water  in  the  opposite  direction.  The  veil  renders  the 
motion  more  vigorous  by  limiting  the  size  of  the  stream,  and  it 
also,  no  dqubt,  helps  to  turn  the  current  to  one  side  or  the  other, 
and  thus  to  direct  the  motions  of  the  animal. 

I  told  you,  at  the  opening  of  my  lecture,  that  some  animals  are 
as  firmly  fixed  to  one  spot  as  an  oak  tree.  The  young  of  such  a 
jelly-fish  as  I  have  just  described,  is  an  illustration  of  this,  as  it  is 
so  much  like  a  plant  that  it  is  often  found  dried  -and  pressed  and 
forming  part  of  a  collection  of  sea-weeds.  The  egg  of  a  jelly-fish 
does  not  hatch  into  a  jelly-fish,  or  even  into  an  animal  which  is  to 
grow  into  a  jelly-fish,  as  the  caterpillar  grows  into  a  butterfly ;  but 
into  an  animal  which,  its  whole  life  through,  has  so  little  resem- 
blance to  its  parent  that  no  one  would  for  an  instant  suspect  the 
relationship,  if  he  knew  nothing  of  the  subject.  The  jelly-fish 
egg  becomes  a  little  trumpet-shaped  animal,  hundreds  of  times 
smaller  than  its  parent,  with  no  umbrella,  no  veil,  and,  after  it  is 
fully  grown,  no  power  of  locomotion.  When  just  hatched  it  swims 
about  for  a  short  time  by  swimming  hairs,  which  cover  its  body. 
It  soon  loses  these,  however,  and  fastening  itself  to  some  object 
such  as  a  stone  or  stick,  it  gives  rise,  like  a  young  plant,  to 
buds,  which  grow,  and  finally  build  up  a  beautiful  branching  tree- 
like community,  with  the  trumpet-shaped  animals  at  the  tips  of  the 
branches  (Fig.  7).  After  a  time  buds  of  a  different  kind  appear 
on  some  of  the  branches.  These  grow  rapidly,  assume  the  bell- 
like  shape  of  jelly-fishes,  and  dropping  off  from  the  branches,  like 
fruit  falling  from  a  tree,  they  swim  off  into  the  water,  and  growing  up, 
become  animals  like  their  grandparents,  but  not  at  all  like  their 
parents.  From  the  eggs  laid  by  these  jelly-fishes  new  tree-like 


86 


Fig.  7.  A  hydroid  Jelly  Fish,  greatly  magnified,  showing  the  fixed  form  and  the 
swimming  form.    Drawn  from  nature  by  W.  K.  Brooks. 


87 

communities  of  hydroids  develop,  to  give  rise  to  jelly-fish  buds  in 
their  turn. 

The  method  of  swimming  by  pumping  a  stream  of  water  seems 
to  be  quite  a  favorite  one  in  nature,  and  we  meet  numerous  modi- 
fications of  it.  One  of  the  more  interesting  is  presented  by  the 
Squid,  or  the  Devil-fish.  The  squid  has  a  long,  slender  body,  and 
a  large  round  head,  and  around  the  mouth  a  number  of  arms, 
which  are  used  in  capturing  prey  and  crawling  over  the  bottom. 
The  mechanism  of  these  arms  is  so  peculiar  that  I  will  say  a  very  few 
words  about  it  before  I  speak  of  the  animal's  swimming  organ. 
The  arms  are  covered  by  rows  of  cup-shaped  suckers,  hundreds 
on  each  arm,  and  in  each  cup  there  is  a  muscular  piston,  which 
can  be  drawn  back  to  form  a  vacuum.  In  order  to  increase  the 
holding  power  of  the  sucking  cups,  a  small  horny  saw,  bent  into  a 
circle,  is  placed,  teeth  outwards,  just  inside  the  edge  of  each  cup. 
In  the  giant  squid,  which  grows  to  a  length  of  fifteen  or  sixteen 
feet,  the  cups  are  several  inches  wide,  and  as  there  are  ten  arms, 
with  several  hundred  cups  on  each  arm,  their  grasping  power  is 
very  great.  Few  animals,  except  a  sperm  whale,  could  break 
from  the  grasp  of  such  an  animal,  or  tear  it  from  its  hold  upon  a 
rocky  bottom. 

The  swimming  organ  of  the  squid,  however,  is  something  quite 
different  from  these  grasping  arms,  and  is  a  sort  of  loose  jacket 
around  the  body,  open  at  the  neck.  In  order  to  understand  the 
form  and  mode  of  action  of  this  swimming  jacket,  suppose  that 
my  body  and  limbs,  as  I  stand  with  my  arms  at  my  sides,  repre- 
sent the  body  of  a  squid,  and  my  head  and  neck  the  same  parts 
of  the  squid.  (Figs.  8,  9.)  Now  suppose  my  whole  body  up  to 
my  neck  to  be  placed  in  a  loose  rubber  bag,  pointed  at  one 
end,  and  open  around  the  neck,  and  suppose  my  body  to  be 
fastened  to  the  bag  along  the  middle  of  my  back.  If,  immersed 
in  water,  I  push  on  the  inside  of  the  bag  with  my  hands  and 
stretch  it  away  from  my  body,  the  water  will,  of  course,  run  in 
around  my  neck,  and  it  will  be  driven  out  again  by  the  elasticity 
of  the  bag  as  soon  as  I  remove  the  pressure.  The  jacket  of  the 
squid  is  worked  by  the  muscles  which  compose  it,  not  by  hands, 
but  otherwise  it  is  fairly  represented  by  this  model. 

The  gills  of  the  squid  are  on  the  sides  of  the  body  inside  the 
jacket,  and  this  is  primarily  a  respiratory  organ  for  pump  ng  water 
to  and  away  from  the  gills,  but  a  slight  modification  turns  it 


88 


Pig.  8.  Adutt  Squid,  much  smaller  than  life.    Copied  from  Verrill. 


Fig.  9.   A  very  young  Squid,  showing  the  jacket  and  siphon ;  greatly  magnified. 
Drawn  from  nature  by  W.  K.  Brooks. 


89 

into  an  efficient  organ  of  locomotion.  Suppose  that  having  fastened 
my  body  into  the  rubber  jacket,  I  cut,  in  a  circle  of  stiff  leather,  a 
little  larger  than  the  opening  of  the  jacket,  a  hole  to  fit  my  neck, 
and  fasten  the  leather  water-tight  around  my  neck,  as  a  flat  hori- 
zontal collar,  and  then  tuck  the  edges  of  the  collar  down  into  the 
mouth  of  the  jacket.  Now  when  I  expand  the  jacket  the  water 
will  pass  into  and  fill  it,  between  its  edge  and  the  edges  of  the 
collar,  but  when  I  remove  the  pressure  the  collar  will  act  as  a 
valve  and  will  be  pushed  out  against  the  jacket  by  the  water, 
preventing  the  escape  of  the  latter.  If  now  I  make  a  small 
hole  under  my  chin  and  fasten  a  short  rubber  hose  and  nozzle  to 
it,  the  elasticity  of  the  jacket  will  drive  a  powerful  stream  through 
it,  and  under  water  I  could  use  this  stream  to  drive  my  body  back- 
wards through  the  water,  or  by  pointing  the  nozzle  a  little  to  one 
side  or  the  other  I  could  guide  my  course  a  little.  The  squid  has 
a  fleshy  collar  around  its  neck,  essentially  like  the  imaginary  one 
of  leather,  and  under  its  head  there  is  a  movable  spout  or  nozzle, 
called  the  siphon,  by  which,  it  can  turn  the  stream  of  water  to  one 
side  or  the  other.  The  water  flows  to  the  gills  through  the  large 
orifice  around  the  edge  of  the  jacket,  but,  as  it  is  discharged 
through  the  very  small  siphon,  the  jet  of  water  is  sufficiently 
powerful  to  drive  the  animal  backwards  with  great  rapidity. 

Fig.  8  is  a  view  of  a  full-grown  squid,  and  Fig.  9  is  a  side-view 
of  a  very  young  one,  copied  from  a  drawing  which  I  made  some 
years  ago  from  a  specimen  which  I  took,  alive,  out  of  an  egg.  As 
the  very  young  squid  is  transparent,  the  collar  and  siphon  can  be 
seen  through  the  transparent  jacket,  and  the  relation  of  these  parts 
will  therefore  be  readily  understood  from  this  figure.  The  large 
mass  at  the  right  in  this  figure  is  the  yolk  of  the  egg,  fastened  like 
a  nursing  bottle  near  the  animal's  mouth. 

In  a  marine  animal  known  as  Salpa,  which  is  often  met  with 
swimming  at  the  surface  of  the  ocean,  we  find  another  modification 
of  the  same  mode  of  motion  by  pumping  water.  (Fig.  10.)  Salpa 
is  shaped  something  like  a  small  barrel  with  an  opening  guarded 
by  valves  at  each  end.  One  set  of  valves  opens  inwards,  and  the 
other  outwards.  The  wall  of  the  barrel  is  elastic,  and  the  barrel 
hoops  are  represented  by  a  number  of  muscular  bands  which  run 
around  it.  In  swimming  the  animal  contracts  these  hoops  and 
empties  the  barrel.  The  muscles  are  then  relaxed,  and  as  the  elas- 
ticity of  the  walls  expands  the  barrel  the  water  flows  in  and  fills  it. 


9o 


I! 

• 


91 

As  the  water  flows  in  at  one  end  and  out  at  the  other,  this  pump- 
ing action  drives  the  animal  along  through  the  water. 

A  comparison  of  Salpa  with  closely  related  animals  shows  us 
that  the  parts  which  effect  the  very  peculiar  mode  of  locomotion  in 
Salpa,  and  which  are  fitted  especially  for  this  use,  exist  in  allied 
animals  in  a  simpler  shape,  and  have  simpler  work  to  do.  Where- 
ever  we  are  able  to  study  in  the  same  way  any  of  the  other  contri- 
vances by  which  motion  is  produced  in  animals,  we  meet  with  the 
same  history.  We  may  state,  as  a  general  truth,  that  wherever 
we  find  any  part  of  the  body  of  an  animal  especially  fitted  for 
some  peculiar  purpose,  careful  study  will  show  us  the  same  part  in 
a  simpler  form  and  doing  a  simpler  sort  of  work  in  some  closely 
related  animal.  The  cilia  which  row  the  slipper  animal  or  the 
snail  larva  through  the  water,  and  which,  at  the  same  time,  sweep 
food  into  the  mouth,  are  almost  exactly  like  the  cilia  which  in  many 
other  animals  simply  set  up  food- currents  in  the  water,  but  have  no 
locomotor  function.  The  pumping  jacket  and  siphon  of  the  squid 
are  only  a  slight  modification  of  the  gill-chamber  of  a  snail,  but  in 
the  snail  the  gill-chamber  is  not  an  organ  of  locomotion,  but  is 
simply  a  pump  to  keep  the  breathing  organs  supplied  with  fresh 
water.  What  can  be  more  different  from  each  other  than  a  digging 
foot  for  burrowing  in  the  mud,  and  an  organ  of  flight;  and  yet  in 
certain  clams  a  slight  change  in  the  burrowing  foot  has  actually 
converted  it  into  an  apparatus  by  which  the  animal  is  enabled  to 
make  short  leaps  through  the  air. 

An  ordinary  clam  or  a  fresh- water  mussel  has  so  little  power  of 
motion  that  very  careful  observation  is  necessary  to  discern 
that  it  moves  at  all.  It  lives  almost  buried  in  the  mud  or  sand, 
and  seems  to  be  pretty  firmly  planted ;  but  if  you  have  looked 
carefully  at  a  clam  at  home  in  the  sand,  you  will  have  noticed  that 
it  lies  at  the  end  of  a  long,  shallow  furrow.  Careful  watching  will 
show  that  this  furrow  is  formed  behind  the  animal  as  it  slowly 
plows  its  way  along. 

When  the  clam  is  opened,  a  tough,  fleshy,  tongue-like  organ, — the 
foot,  is  found  inside  the  shell  under  the  soft  body.  The  foot  is  not 
supported  by  bone,  but  is  a  soft  mass  of  muscles  something  like  a 
man's  tongue.  Like  the  tongue  it  can  change  its  shape,  bending 
from  side  to  side,  and  becoming  long  and  slender  and  pointed,  or 
short  and  thick.  It  is  hung  inside  the  shell  by  four  stout  muscles, 


92 

which  form  a  sort  of  sling  for  the  foot,  and  are  attached  to  the  in- 
side of  each  shell  near  its  ends.  When  the  clam  wishes  to  move 
it  relaxes  these  four  muscles,  which  are  known  as  the  foot-retractor 
muscles.  Certain  other  muscles  of  the  foot  then  contract  until  it 
becomes  long,  thin  and  pointed.  The  point  is  now  protruded 
from  between  the  edges  of  the  opened  shell,  and  is  worked  along 
into  the  sand  until  it  is  fully  extended.  It  then  changes  its  shape. 
The  tip  which  has  been  thin  and  sharp  now  swells  out,  and  acts  as 
an  anchor,  by  which  the  animal  is  firmly  fastened  into  the  sand. 
The  foot-retractor  muscles  now  contract.  If  the  tip  of  the  foot 
were  free  it  would  be  pulled  into  the  shell,  but  as  it  is  fastened  into 
the  sand,  the  retractor  muscles,  instead  of  pulling  the  foot  back, 
draw  the  whole  body  and  shell  through  the  sand  up  to  the  tip  of 
the  foot.  This  then  changes  its  shape  once  more,  and  becomes 
thin  and  spade-like ;  and  the  retractor  muscles  relaxing  again,  it 
works  its  way  forwards  into  the  sand.  Then  changing  to  an 
anchor  once  more,  it  serves  as  a  fixed  point  to  which  the  retractor 
muscles  again  drag  the  body  and  shell.  The  sand  is  very  heavy, 
and  this  plowing  method  of  locomotion  is  necessarily  very  slow, 
but  it  is  plain  that  if  the  animal  were  to  perform  the  same  motions 
in  water,  with  sufficient  rapidity,  it  might  swim  a  little,  since  the 
expanded  tip  of  the  foot  would  be  resisted  by  the  water,  and  would 
take  hold  exactly  as  it  does  in  the  sand. 

Many  clams  do  swim  a  little  in  this  way,  jerking  themselves  for 
short  distances  through  the  water  by  violently  pulling  back  the 
extended  foot.  In  one  of  our  small  marine  clams,  Yoldia,  the  foot 
is  slightly  changed  to  fit  it  for  this  new  use.  The  tip  is  split 
vertically,  so  that  the  halves  may  be  spread  apart  like  an  open 
book,  or  they  may  be  folded  together.  In  swimming,  the  animal 
shuts  the  tip  of  its  foot  together,  and  after  extending  it  to  its  full 
length,  opens  the  tip.  Then  violently  contracting  its  retractor 
muscles,  it  jerks  its  foot  back  into  the  shell,  at  the  same  time  dart- 
ing forwards  through  the  water.  The  swimming  Yoldia.  may  be 
compared  to  a  man  swimming  by  means  of  an  umbrella  which  he 
closes  and  pushes  forwards,  and  then  opening  it,  pulls  it  towards 
himself.  The  locomotor  power  of  Yoldia  is  so  highly  developed 
that  it  is  not  only  able  to  swim  about  in  the  water,  but  also  to 
make  leaps  of  eight  or  ten  times  its  own  length  through  the  air, 
and  it  might  be  appropriately  called  the  "  flying  clam."  The  re- 


93 

semblance  between  an  ordinary  burrowing  clam  and  the  flying 
clam  is  so  complete  that  careful  study  would  convince  any  one 
that  the  latter  is  only  an  ordinary  burrowing  clam  which  has  been 
fitted  for  a  swimming  life  by  a  slight  change  which  has  converted 
its  digging  foot  into  a  swimming  organ. 

I  have  now  sketched  very  rapidly  some  of  the  changes  through 
which  an  ordinary  swimming  clam  like  Yoldia  might  be  formed  from 
an  ordinary  burrowing  clam.  I  will  ask  you  to  take  my  word  for  it 
that  careful  study  of  any  other  adaptation  of  an  animal  to  its  surround- 
ings would  lead  to  the  same  result :  the  discovery  of  the  same  part  in 
a  simpler  form  and  doing  simpler  work  in  related  animals.  This 
fact,  with  many  others  which  I  have  no  time  to  present  to  you  at 
present,  has  convinced  many  thoughtful  students  of  nature  that 
the  ingenious  devices  and  efficient  machinery  which  we  meet 
everywhere  in  nature,  fitting  animals  for  their  life,  and  adapting 
them  to  their  surroundings,  have  actually  been  produced  by  the 
slow  change  and  improvement  of  the  simpler  parts  of  their  ances- 
tors. Now  is  this  conclusion  an  explanation  of  these  adaptations  ? 
For  my  own  part  I  fully  accept  the  conclusion,  but  so  far  is  it  from 
being  an  explanation,  that  a  very  little  thought  will  show  that  it  is 
nothing  of  the  kind.  Even  if  I  could  do,  what  is  quite  impossible, 
and  bring  with  me  and  show  you  a  digging  clam  which  was  under- 
going the  change  into  a  swimming  Yoldia,  I  should  simply  show 
you  a  change.  The  exhibition  of  the  change  would  not  be  an 
explanation  of  it.  An  obscure  or  complicated  or  unfamiliar 
change  is  explained  by  pointing  out  its  resemblance  to  something 
which  is  more  familiar  or  more  easy  to  understand.  If  I  can  show 
you  that  the  change  of  an  ordinary  Tunicate  into  a  form  like  Salpa, 
or  the  change  of  a  digging  clam  into  one  which  is  fitted  like  Yoldia 
for  swimming,  is  matched  by  a  change  with  which  you  are  perfectly 
familiar,  I  shall  then  have  given  an  explanation  of  the  origin  of  the 
swimming  machinery  of  Salpa  or  of  Yoldia.  I  have  no  hope  of 
getting  to  the  bottom  of  the  subject,  or  of  giving  a  complete 
explanation  of  this  or  anything  else,  but  I  do  hope  to  show  you 
that  it  is  no  more  incomprehensible  than  things  which  are  as 
familiar  to  you  as  the  falling  of  an  apple.  To  do  this  I  shall  be 
compelled  to  talk  a  little  on  things  which  may  not  at  first  seem  to 
have  much  to  do  with  the  subject.  I  must  ask  you  to  pay  careful 
attention  and  trust  me  to  bring  things  together  before  I  close. 


94 

If  left  to  themselves  all  living  things  would  tend  to  increase  with 
marvellous  rapidity.  No  living  thing  is  left  entirely  to  itself,  for 
the  world  is  crowded,  and  every  plant  and  every  animal  has  to 
work  for  its  living  and  fight  for  its  place.  Those  which  fall  a  prey 
to  enemies  or  are  crowded  out  by  competitors  are  always  much 
more  numerous  than  those  which  flourish  and  live  their  lives 
through.  It  is  clear  that  if  every  acorn  or  beechnut  grew  up  into 
a  forest  tree  the  whole  earth  would  be  covered  in  a  few  genera- 
tions, and  all  other  trees  and  plants  would  be  crowded  out.  It  is 
plain,  too,  that  if  each  one  of  the  millions  of  eggs  laid  each  year  by 
each  female  codfish  were  to  live  and  develop  into  a  full-grown  fish, 
the  whole  ocean  would  soon  be  filled  with  codfish.  A  little  exam- 
ination will  show  that  this  is  true  of  all  .animals  and  plants,  that  the 
oak  and  the  codfish  are  not  exceptional,  but  that  the  slowest 
breeders  tend  to  increase  at  such  a  rate  that  they  would  soon 
cover  the  whole  earth  if  they  were  left  to  themselves. 

A  young  lion's  chance  of  growing  up  and  living  through  its 
natural  life  is  unusually  favorable.  The  strong  parental  instinct 
leads  both  lion  and  lioness  to  guard  and  protect  the  young.  As 
only  two  or  three  young  are  born  at  a  time,  these  are  sure  of  ample 
care  and  attention  from  their  parents  until  they  are  able  to  shift  for 
themselves.  The  great  strength  of  the  lull-grown  lion,  added  to 
the  care  and  education  which  it  receives  from  its  parents,  ought  to 
fit  it  for  holding  its  place  in  the  world  and  for  living  out  its  natural 
life,  as  well  as  for  rearing  its  young  and  giving  them  the  same 
favorable  start.  We  should  therefore  expect  to  find  the  number  of 
lions  which  grow  up  and  have  children  about  as  great  as  the  num- 
ber which  are  born,  but  nothing  could  be  further  from  the  truth. 
Some  years  ago,  when  time  hung  heavily  on  my  hands,  I  set  my- 
self the  following  problem,  partly  from  my  interest  in  the  subject 
and  partly  as  a  puzzle.  If  a  single  lion  and  lioness  had  been  placed 
on  the  earth  four  thousand  years  ago,  had  lived  for  thirty  years,  and 
each  year,  from  the  tenth  to  the  twentieth,  had  given  birth  to  two 
young ;  if  each  of  these  young  had  lived  for  thirty  years,  and  if 
each  pair  had  borne  two  young  annually  for  the  ten  years  of  their 
prime,  and  so  on  ;  if  no  lion  had  ever  died  from  accident  or  hard- 
ship, but  all  had  lived  out  their  natural  life,  what  would  be  the 
number  of  lions  in  the  present  generation  ?  I  am  afraid  to  give 
you  the  answer,  but  you  can  figure  it  out  for  yourselves  if  you 
choose.  I  will  only  say  that  the  lions  of  this  generation  would  fill 


95 

up  the  whole  ocean  and  cover  the  whole  earth,  and  that  they  would 
have  to  stand  upon  each  other,  layer  upon  layer,  until  they  formed 
a  ball  hundreds  of  thousands  of  miles  in  diameter,  with  the  earth 
like  a  little  core  in  the  centre,  and  the  moon  buried  deeply  under 
the  surface.  This  case  shows  that  even  the  slowest  breeders  would 
soon  stock  the  entire  earth  if  all  the  individuals  which  are  born 
should  grow  up  to  maturity. 

It  is  plain  then  that  the  world  is  overstocked,  and  that  each  ani- 
mal must  work  and  fight  for  existence.  Every  living  thing  finds 
itself  at  birth  face  to  face  with  the  problem  how  to  make  a  place  for 
itself  in  this  crowded  world ;  how  to  escape  its  enemies  and  van- 
quish its  competitors  ;  how  to  secure  its  proper  share  of  food  and 
air  and  standing  room,  for  itself  and  for  its  children.  Man  is  a 
living  thing,  and  he  is  no  exception  to  this  universal  rule.  We  find 
ourselves  thrust  without  our  consent  into  a  crowded  world,  where 
food  is  scarce  and  employment  hard  to  find.  Other  mouths  are 
open  to  snatch  our  share  of  food,  and  other  hands  are  stretched 
out,  eager  to  do  our  work  and  to  crowd  us  out  of  our  places.  Each 
one  of  us  is  constantly  brought  face  to  face  with  the  question :  How 
shall  I  distance  my  competitors  and  get  and  hold  on  to  my  share 
of  the  necessaries  and  comforts  of  life  ?  How  shall  I  make  a  place 
in  the  world  for  myself  and  my  children  ?  Every  moment  each  of 
us  finds  this  vital  question  staring  him  in  the  face,  and  I  think  that 
most  of  us  have  recognized  that  this  is  the  true  answer :  Make 
yourself  a  little  different  from  your  neighbors.  We  may  never 
have  put  it  into  these  words,  and  they  may  not  seem  very  clear  at 
first,  but  you  will  all  agree  with  me  that  just  so  soon  as  a  man  learns 
to  do  for  his  neighbors  some  useful  thing  which  they  cannot  do  for 
themselves,  or  learns  to  do  his  work  better  or  more  rapidly  or  more 
easily  than  his  competitors,  that  man  need  have  no  fear  of  the 
struggle  for  existence,  until  his  competitors  overtake  and  pass 
him.  It  makes  no  difference  what  the  useful  thing  is — making 
shoes  or  curing  the  sick  ;  the  man  who  can  do  his  work  better  or 
more  cheaply  than  his  neighbors  may,  with  health  and  industry, 
always  demand  in  return,  contributions  from  their  shares  of  the 
necessaries  and  conveniences  of  life. 

How  is  it  that  hundreds  of  thousands  of  people  are  able  to  live 
upon  a  few  square  miles,  here  in  Baltimore,  in  health  and  comfort, 
while  a  few  scattered  savages  are  barely  able  to  preserve  life  upon  an 
area  of  hundreds  of  miles  in  the  fertile  plains  of  South  America 


96 

or  of  the  West  ?  How  is  it  that  there  is  always  room  here  for 
more ;  that  our  children  grow  up  and  find  places  for  themselves, 
and  that  scarcely  any  one  actually  dies  of  want,  while  death  from 
starvation  and  exposure  is  not  at  all  unusual  among  savages? 
Training  is  the  explanation.  One  savage  is  hardly  different  f^m 
another,  and  each  is  as  well  able  as  his  neighbors  to  supply  his  own 
wants  of  all  kinds ;  while  with  us  one  man  is  a  farmer,  another  a 
merchant ;  one  learns  a  trade  and  another  studies  a  profession. 
Each  one  prepares  himself,  by  long  training,  to  do  for  his  neighbors 
some  one  useful  thing  which  they  cannot  do  as  well  for  themselves, 
and  in  this  way  to  work  out  and  hold  fast  to  a  place  in  the  world. 
Every  year  this  difference  between  man  and  man  grows  greater, 
and  it  is  due  to  this,  and  to  this  alone,  that  our  country  is  able  to 
support  in  comfort  a  great  and  growing  community,  instead  of  a 
few  scattered  and  struggling  savages. 

Now  what  is  true  of  man  in  this  particular  is  true  of  every  other 
living  thing :  there  is  only  one  way  for  any  of  them  to  escape  com- 
petition and  work  out  a  place  for  itself  in  the  world ;  and  this  way 
is  for  it  to  become  in  some  way  slightly  different  from  its  competi- 
tors. That  the  amount  of  life  which  the  earth  can  support  in- 
creases as  the  diversity  of  the  forms  of  life  increases  may  be  shown 
by  an  illustration.  Suppose  that  a  limited  area,  an  island  for 
instance,  is  peopled  by  a  race  of  farmers,  and  that  each  fanner 
is  also  his  own  mechanic,  making  and  repairing  his  own  tools, 
building  his  own  houses,  and  spinning  his  own  clothing,  as  well  as 
cultivating  his  land.  Let  this  farming  community  increase  until 
all  the  land  is  occupied,  and  each  person  has  only  enough  to  sup- 
ply his  own  wants.  Now  how  shall  we  find  room  for  any  more 
people,  in  the  island,  after  all  the  room  is  occupied  ?  By  simply 
dividing  the  community  into  two  classes,  mechanics  and  farmers. 
As  the  farmer  can  now  have  his  house  and  clothing  made  by  others, 
he  can  give  all  his  time  to  the  cultivation  of  his  land,  and  he  will 
soon  become  more  completely  acquainted  with  his  business  than 
he  could  possibly  have  been  when  half  his  time  and  attention  was 
given  to  other  subjects.  As  his  tools  and  implements  are  now 
made  by  a  man  who  has  given  time  and  study  to  the  subject,  the 
farmer  can  do  better  work  with  them  than  he  could  with  such  rude 
tools  as  he  could  make  for  himself.  We  shall  now  have  a  more 
intelligent  farmer,  working  with  better  tools,  and  having  more  time 
to  devote  to  his  work;  and  the  result  of  this  improvement  in  the 


97 

cultivation  of  the  land  will  be  such  an  increase  in  fertility  that  the 
island  will  now  readily  support  all  its  farmers  and  all  its  mechanics, 
with  room  to  spare  for  others.  We  see  then  that  if  we  can  replace 
a  single  class  of  men  all  of  whom  have  some  knowledge  of  farm- 
ing and  some  mechanical  skill,  by  two  classes,  good  farmers  and  good 
n,  Panics,  we  shall  at  the  same  time  increase  the  population  which 
the  country  can  support.  If  any  particular^kind  of  plant  or  animal 
has  increased  until  no  more  individuals  can  find  places,  the  amount 
of  life  might  be  still  further  increased  if  we  could  put  in  the  place 
of  this  living  thing  two  slightly  different  kinds. 

Now  how  can  this  be  accomplished  ?  Each  plant  or  each  animal 
has  children  like  itself,  but  careful  study  shows  that  the  likeness 
of  children  to  parents  is  never  quite  perfect,  but  that  the  children 
vary  slightly,  although  they  as  a  rule  resemble  their  own  parents 
more  than  they  do  other  animals  or  plants  of  the  same  kind.  While 
the  difference  between  parent  and  child  is  very  slight,  the  varia- 
tion may  be  in  any  direction  whatever. 

Suppose  then  that  a  certain  kind  of  animal  is  so  abundant 
that  there  is  no  room  for  any  more  individuals,  but  that  one 
must  die  for  each  young  one  which  grows  up.  Now  suppose  that 
one  of  these  animals  gives  birth  to  a  number  of  young,  which 
differ  slightly  from  the  others  in  such  a  way  that  they  are  able 
to  capture  some  article  of  food  which  the  others  cannot  capture, 
or  to  reach  and  inhabit  places  which  the  others  cannot  reach,  or 
to  escape  enemies  which  are  destructive  to  the  others,  or  to  gain 
a  similar  advantage  in  some  other  way.  It  is  plain  that  these 
animals  will  grow  up  and  flourish,  and  will  leave  many  children, 
and  as  the  offspring  resembles  its  parents  more  than  it  does 
other  animals,  these  children  will,  as  a  rule,  share  this  advantage, 
and  the  new  race  will  therefore  increase  at  the  expense  of  the  old 
unimproved  form.  The  only  way  in  which  the  latter  can  hold  its 
place  at  all  is  by  escaping  from  competition  with  the  improved 
form,  by  itself  improving  in  a  different  direction.  We  shall,  there- 
fore, have  two  slightly  different  races  of  animals  in  place  of  a 
single  old  form,  and  the  number  of  individuals  in  these  two  races 
together  may  be  very  much  greater  than  the  greatest  number  of 
individuals  of  the  old  race. 

The  rate  of  increase  in  animals  is  so  rapid  that  in  a  few  gene- 
rations the  country  will  become  fully  stocked  with  both  of  the 
improved  races,  and  all  their  advantage  will  be  lost.  Each  of 


them  will  be  in  the  position  of  a  man  who,  at  one  time  the 
acknowledged  leader  in  his  business,  has  lost  his  lead  and  has 
allowed  his  competitors  to  catch  up  with  him.  The  only  rem- 
edy is  for  each  race  to  divide  up  again,  and  for  each  division  to 
escape  competition  with  the  other  by  variation  and  improve- 
ment in  a  new  direction.  This  process  is  going  on  continually 
among  all  kinds  of  Hying  things,  and  its  result  is  the  endless 
diversity  of  life  ;  the  infinite  variety  of  contrivances  by  which  the 
wants  of  living  things  are  supplied  ;  the  mechanism  by  which 
some  capture  their  food  in  the  air,  while  others  are  fitted  for  life  in 
the  water,  or  among  the  tree-tops,  or  on  the  ground,  or  under  the 
ground  ;  the  constitution  which  fits  one  animal  for  life  in  the 
tropics  and  another  for  life  in  the  arctic  regions  ;  the  instinct  which 
teaches  one  animal  to  find  abundant  food  where  another  would 
starve  ;  or  the  agility  or  cunning  or  skill  which  enables  one  animal 
to  live  securely  among  enemies  to  which  another  animal  would 
quickly  fall  a  victim. 

It  is  often  said  that  as  our  knowledge  of  nature  increases,  we 
grow  in  admiration  and  reverence  for  the  great  Cause  to  which  all 
nature  owes  its  existence.  This  is  certainly  so  in  this  case.  We  find 
ourselves  thrust  without  our  consent  into  a  world  which  is  already 
overstocked.  We  find  that  there  is  no  place  for  us  without 
constant  work  ;  labor  and  bitter  competition  are  everywhere  around 
us.  There  is  110  escape  from  them.  We  feel  that  all  this  might  have 
been  better  arranged  ;  that  the  world  owes  us  a  living,  and  that  an 
easy  way  to  gain  it  ought  to  be  provided.  This  weary  struggle 
for  life  seems  so  bitter  and  so  unjust  that  it  is  not  strange  that  men 
should  have  believed,  in  old  times,  that  labor  is  a  curse  laid  upon 
man  for  his  sins.  Npw-a-days,  thanks  to  a  wider  knowledge  of 
the  world  around  us,  we  know  that  while  the  world  does  owe  a 
living  to  every  living  thing  which  can  find  a  place  upon  it,  it  owes 
this  living  only  to  those  who  show  themselves  worthy,  by  progress 
and  improvement.  Thanks  to  natural  science  we  now  know  that 
far  from  being  a  curse,  labor,  and  the  competition  and  improve- 
ment which  come  from  the  necessity  for  labor,  have  been  the 
means  by  which  all  the  endless  diversity  of  life  upon  the  earth  has 
been  produced  :  and  the  one  lesson  which  natural  science  teaches, 
above  everything  else,  was  summed  up  ages  ago  by  the  wise 
preacher  in  the  words,  "  Whatsoever  thy  hand  findeth  to  do,  do  it 
with  thy  might." 


THE 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
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DAY  AND  1P»«$J.tfO^  2!LJ"1F  •£y£HIHMkBAY 
OVERDUE.  I 


MAR  2?  1939 

.  ,       •      ,    •  ;     •  . 

APR  2  5  1957 

. 

?!••  -.  '      ~ 

1 

LD  21-95m-7,'37 

